diff --git a/backend/src/controllers/error-helper.ts b/backend/src/controllers/error-helper.ts
new file mode 100644
index 00000000..a902560f
--- /dev/null
+++ b/backend/src/controllers/error-helper.ts
@@ -0,0 +1,18 @@
+import { BadRequestException } from '../exceptions/bad-request-exception.js';
+
+/**
+ * Checks for the presence of required fields and throws a BadRequestException
+ * if any are missing.
+ *
+ * @param fields - An object with key-value pairs to validate.
+ */
+export function requireFields(fields: Record<string, unknown>): void {
+    const missing = Object.entries(fields)
+        .filter(([_, value]) => value === undefined || value === null || value === '')
+        .map(([key]) => key);
+
+    if (missing.length > 0) {
+        const message = `Missing required field${missing.length > 1 ? 's' : ''}: ${missing.join(', ')}`;
+        throw new BadRequestException(message);
+    }
+}
diff --git a/backend/src/controllers/students.ts b/backend/src/controllers/students.ts
index 54aae143..51488a2a 100644
--- a/backend/src/controllers/students.ts
+++ b/backend/src/controllers/students.ts
@@ -1,100 +1,67 @@
 import { Request, Response } from 'express';
 import {
+    createClassJoinRequest,
     createStudent,
+    deleteClassJoinRequest,
     deleteStudent,
     getAllStudents,
+    getJoinRequestByStudentClass,
+    getJoinRequestsByStudent,
     getStudent,
     getStudentAssignments,
     getStudentClasses,
     getStudentGroups,
+    getStudentQuestions,
     getStudentSubmissions,
 } from '../services/students.js';
-
+import { requireFields } from './error-helper.js';
 import { StudentDTO } from '@dwengo-1/common/interfaces/student';
 
-// TODO: accept arguments (full, ...)
-// TODO: endpoints
 export async function getAllStudentsHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
 
-    const students = await getAllStudents(full);
+    const students: StudentDTO[] | string[] = await getAllStudents(full);
 
-    if (!students) {
-        res.status(404).json({ error: `Student not found.` });
-        return;
-    }
-
-    res.json({ students: students });
+    res.json({ students });
 }
 
 export async function getStudentHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    const student = await getStudent(username);
 
-    const user = await getStudent(username);
-
-    if (!user) {
-        res.status(404).json({
-            error: `User with username '${username}' not found.`,
-        });
-        return;
-    }
-
-    res.json(user);
+    res.json({ student });
 }
 
 export async function createStudentHandler(req: Request, res: Response): Promise<void> {
+    const username = req.body.username;
+    const firstName = req.body.firstName;
+    const lastName = req.body.lastName;
+    requireFields({ username, firstName, lastName });
+
     const userData = req.body as StudentDTO;
 
-    if (!userData.username || !userData.firstName || !userData.lastName) {
-        res.status(400).json({
-            error: 'Missing required fields: username, firstName, lastName',
-        });
-        return;
-    }
-
-    const newUser = await createStudent(userData);
-
-    if (!newUser) {
-        res.status(500).json({
-            error: 'Something went wrong while creating student',
-        });
-        return;
-    }
-
-    res.status(201).json(newUser);
+    const student = await createStudent(userData);
+    res.json({ student });
 }
 
 export async function deleteStudentHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
-
-    const deletedUser = await deleteStudent(username);
-    if (!deletedUser) {
-        res.status(404).json({
-            error: `User with username '${username}' not found.`,
-        });
-        return;
-    }
-
-    res.status(200).json(deletedUser);
+    const student = await deleteStudent(username);
+    res.json({ student });
 }
 
 export async function getStudentClassesHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
-    const username = req.params.id;
+    const username = req.params.username;
+    requireFields({ username });
 
     const classes = await getStudentClasses(username, full);
 
-    res.json({ classes: classes });
+    res.json({ classes });
 }
 
 // TODO
@@ -103,33 +70,75 @@ export async function getStudentClassesHandler(req: Request, res: Response): Pro
 // Have this assignment.
 export async function getStudentAssignmentsHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
-    const username = req.params.id;
+    const username = req.params.username;
+    requireFields({ username });
 
     const assignments = getStudentAssignments(username, full);
 
-    res.json({
-        assignments: assignments,
-    });
+    res.json({ assignments });
 }
 
 export async function getStudentGroupsHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
-    const username = req.params.id;
+    const username = req.params.username;
+    requireFields({ username });
 
     const groups = await getStudentGroups(username, full);
 
-    res.json({
-        groups: groups,
-    });
+    res.json({ groups });
 }
 
 export async function getStudentSubmissionsHandler(req: Request, res: Response): Promise<void> {
-    const username = req.params.id;
+    const username = req.params.username;
     const full = req.query.full === 'true';
+    requireFields({ username });
 
     const submissions = await getStudentSubmissions(username, full);
 
-    res.json({
-        submissions: submissions,
-    });
+    res.json({ submissions });
+}
+
+export async function getStudentQuestionsHandler(req: Request, res: Response): Promise<void> {
+    const full = req.query.full === 'true';
+    const username = req.params.username;
+    requireFields({ username });
+
+    const questions = await getStudentQuestions(username, full);
+
+    res.json({ questions });
+}
+
+export async function createStudentRequestHandler(req: Request, res: Response): Promise<void> {
+    const username = req.params.username;
+    const classId = req.body.classId;
+    requireFields({ username, classId });
+
+    const request = await createClassJoinRequest(username, classId);
+    res.json({ request });
+}
+
+export async function getStudentRequestsHandler(req: Request, res: Response): Promise<void> {
+    const username = req.params.username;
+    requireFields({ username });
+
+    const requests = await getJoinRequestsByStudent(username);
+    res.json({ requests });
+}
+
+export async function getStudentRequestHandler(req: Request, res: Response): Promise<void> {
+    const username = req.params.username;
+    const classId = req.params.classId;
+    requireFields({ username, classId });
+
+    const request = await getJoinRequestByStudentClass(username, classId);
+    res.json({ request });
+}
+
+export async function deleteClassJoinRequestHandler(req: Request, res: Response): Promise<void> {
+    const username = req.params.username;
+    const classId = req.params.classId;
+    requireFields({ username, classId });
+
+    const request = await deleteClassJoinRequest(username, classId);
+    res.json({ request });
 }
diff --git a/backend/src/controllers/teachers.ts b/backend/src/controllers/teachers.ts
index c3894bd6..9275ca92 100644
--- a/backend/src/controllers/teachers.ts
+++ b/backend/src/controllers/teachers.ts
@@ -4,137 +4,97 @@ import {
     deleteTeacher,
     getAllTeachers,
     getClassesByTeacher,
-    getQuestionsByTeacher,
+    getJoinRequestsByClass,
     getStudentsByTeacher,
     getTeacher,
+    getTeacherQuestions,
+    updateClassJoinRequestStatus,
 } from '../services/teachers.js';
+import { requireFields } from './error-helper.js';
 import { TeacherDTO } from '@dwengo-1/common/interfaces/teacher';
 
 export async function getAllTeachersHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
 
-    const teachers = await getAllTeachers(full);
+    const teachers: TeacherDTO[] | string[] = await getAllTeachers(full);
 
-    if (!teachers) {
-        res.status(404).json({ error: `Teacher not found.` });
-        return;
-    }
-
-    res.json({ teachers: teachers });
+    res.json({ teachers });
 }
 
 export async function getTeacherHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    const teacher = await getTeacher(username);
 
-    const user = await getTeacher(username);
-
-    if (!user) {
-        res.status(404).json({
-            error: `Teacher '${username}' not found.`,
-        });
-        return;
-    }
-
-    res.json(user);
+    res.json({ teacher });
 }
 
 export async function createTeacherHandler(req: Request, res: Response): Promise<void> {
+    const username = req.body.username;
+    const firstName = req.body.firstName;
+    const lastName = req.body.lastName;
+    requireFields({ username, firstName, lastName });
+
     const userData = req.body as TeacherDTO;
 
-    if (!userData.username || !userData.firstName || !userData.lastName) {
-        res.status(400).json({
-            error: 'Missing required fields: username, firstName, lastName',
-        });
-        return;
-    }
-
-    const newUser = await createTeacher(userData);
-
-    if (!newUser) {
-        res.status(400).json({ error: 'Failed to create teacher' });
-        return;
-    }
-
-    res.status(201).json(newUser);
+    const teacher = await createTeacher(userData);
+    res.json({ teacher });
 }
 
 export async function deleteTeacherHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
-
-    const deletedUser = await deleteTeacher(username);
-    if (!deletedUser) {
-        res.status(404).json({
-            error: `User '${username}' not found.`,
-        });
-        return;
-    }
-
-    res.status(200).json(deletedUser);
+    const teacher = await deleteTeacher(username);
+    res.json({ teacher });
 }
 
 export async function getTeacherClassHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
     const full = req.query.full === 'true';
-
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    requireFields({ username });
 
     const classes = await getClassesByTeacher(username, full);
 
-    if (!classes) {
-        res.status(404).json({ error: 'Teacher not found' });
-        return;
-    }
-
-    res.json({ classes: classes });
+    res.json({ classes });
 }
 
 export async function getTeacherStudentHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
     const full = req.query.full === 'true';
-
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    requireFields({ username });
 
     const students = await getStudentsByTeacher(username, full);
 
-    if (!students) {
-        res.status(404).json({ error: 'Teacher not found' });
-        return;
-    }
-
-    res.json({ students: students });
+    res.json({ students });
 }
 
 export async function getTeacherQuestionHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
     const full = req.query.full === 'true';
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    const questions = await getTeacherQuestions(username, full);
 
-    const questions = await getQuestionsByTeacher(username, full);
-
-    if (!questions) {
-        res.status(404).json({ error: 'Teacher not found' });
-        return;
-    }
-
-    res.json({ questions: questions });
+    res.json({ questions });
+}
+
+export async function getStudentJoinRequestHandler(req: Request, res: Response): Promise<void> {
+    const username = req.query.username as string;
+    const classId = req.params.classId;
+    requireFields({ username, classId });
+
+    const joinRequests = await getJoinRequestsByClass(classId);
+    res.json({ joinRequests });
+}
+
+export async function updateStudentJoinRequestHandler(req: Request, res: Response): Promise<void> {
+    const studentUsername = req.query.studentUsername as string;
+    const classId = req.params.classId;
+    const accepted = req.body.accepted !== 'false'; // Default = true
+    requireFields({ studentUsername, classId });
+
+    const request = await updateClassJoinRequestStatus(studentUsername, classId, accepted);
+    res.json({ request });
 }
diff --git a/backend/src/data/classes/class-join-request-repository.ts b/backend/src/data/classes/class-join-request-repository.ts
index 1cd0288c..0d9ab6e1 100644
--- a/backend/src/data/classes/class-join-request-repository.ts
+++ b/backend/src/data/classes/class-join-request-repository.ts
@@ -2,13 +2,17 @@ import { DwengoEntityRepository } from '../dwengo-entity-repository.js';
 import { Class } from '../../entities/classes/class.entity.js';
 import { ClassJoinRequest } from '../../entities/classes/class-join-request.entity.js';
 import { Student } from '../../entities/users/student.entity.js';
+import { ClassJoinRequestStatus } from '@dwengo-1/common/util/class-join-request';
 
 export class ClassJoinRequestRepository extends DwengoEntityRepository<ClassJoinRequest> {
     public async findAllRequestsBy(requester: Student): Promise<ClassJoinRequest[]> {
         return this.findAll({ where: { requester: requester } });
     }
     public async findAllOpenRequestsTo(clazz: Class): Promise<ClassJoinRequest[]> {
-        return this.findAll({ where: { class: clazz } });
+        return this.findAll({ where: { class: clazz, status: ClassJoinRequestStatus.Open } }); // TODO check if works like this
+    }
+    public async findByStudentAndClass(requester: Student, clazz: Class): Promise<ClassJoinRequest | null> {
+        return this.findOne({ requester, class: clazz });
     }
     public async deleteBy(requester: Student, clazz: Class): Promise<void> {
         return this.deleteWhere({ requester: requester, class: clazz });
diff --git a/backend/src/data/questions/question-repository.ts b/backend/src/data/questions/question-repository.ts
index 596b562c..2d165abc 100644
--- a/backend/src/data/questions/question-repository.ts
+++ b/backend/src/data/questions/question-repository.ts
@@ -54,4 +54,11 @@ export class QuestionRepository extends DwengoEntityRepository<Question> {
             orderBy: { timestamp: 'ASC' },
         });
     }
+
+    public async findAllByAuthor(author: Student): Promise<Question[]> {
+        return this.findAll({
+            where: { author },
+            orderBy: { timestamp: 'DESC' }, // New to old
+        });
+    }
 }
diff --git a/backend/src/data/themes.ts b/backend/src/data/themes.ts
index b0fc930c..0a2272e6 100644
--- a/backend/src/data/themes.ts
+++ b/backend/src/data/themes.ts
@@ -1,7 +1,4 @@
-export interface Theme {
-    title: string;
-    hruids: string[];
-}
+import { Theme } from '@dwengo-1/common/interfaces/theme';
 
 export const themes: Theme[] = [
     {
diff --git a/backend/src/interfaces/answer.ts b/backend/src/interfaces/answer.ts
index 5599839f..1f0d0625 100644
--- a/backend/src/interfaces/answer.ts
+++ b/backend/src/interfaces/answer.ts
@@ -1,5 +1,5 @@
 import { mapToUserDTO } from './user.js';
-import { mapToQuestionDTO, mapToQuestionId } from './question.js';
+import { mapToQuestionDTO, mapToQuestionDTOId } from './question.js';
 import { Answer } from '../entities/questions/answer.entity.js';
 import { AnswerDTO, AnswerId } from '@dwengo-1/common/interfaces/answer';
 
@@ -16,10 +16,10 @@ export function mapToAnswerDTO(answer: Answer): AnswerDTO {
     };
 }
 
-export function mapToAnswerId(answer: AnswerDTO): AnswerId {
+export function mapToAnswerDTOId(answer: Answer): AnswerId {
     return {
         author: answer.author.username,
-        toQuestion: mapToQuestionId(answer.toQuestion),
-        sequenceNumber: answer.sequenceNumber,
+        toQuestion: mapToQuestionDTOId(answer.toQuestion),
+        sequenceNumber: answer.sequenceNumber!,
     };
 }
diff --git a/backend/src/interfaces/question.ts b/backend/src/interfaces/question.ts
index 57778bac..48d64f11 100644
--- a/backend/src/interfaces/question.ts
+++ b/backend/src/interfaces/question.ts
@@ -1,16 +1,21 @@
 import { Question } from '../entities/questions/question.entity.js';
 import { mapToStudentDTO } from './student.js';
 import { QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
+import { LearningObjectIdentifier } from '@dwengo-1/common/interfaces/learning-content';
+
+function getLearningObjectIdentifier(question: Question): LearningObjectIdentifier {
+    return {
+        hruid: question.learningObjectHruid,
+        language: question.learningObjectLanguage,
+        version: question.learningObjectVersion,
+    };
+}
 
 /**
  * Convert a Question entity to a DTO format.
  */
 export function mapToQuestionDTO(question: Question): QuestionDTO {
-    const learningObjectIdentifier = {
-        hruid: question.learningObjectHruid,
-        language: question.learningObjectLanguage,
-        version: question.learningObjectVersion,
-    };
+    const learningObjectIdentifier = getLearningObjectIdentifier(question);
 
     return {
         learningObjectIdentifier,
@@ -21,9 +26,11 @@ export function mapToQuestionDTO(question: Question): QuestionDTO {
     };
 }
 
-export function mapToQuestionId(question: QuestionDTO): QuestionId {
+export function mapToQuestionDTOId(question: Question): QuestionId {
+    const learningObjectIdentifier = getLearningObjectIdentifier(question);
+
     return {
-        learningObjectIdentifier: question.learningObjectIdentifier,
+        learningObjectIdentifier,
         sequenceNumber: question.sequenceNumber!,
     };
 }
diff --git a/backend/src/interfaces/student-request.ts b/backend/src/interfaces/student-request.ts
new file mode 100644
index 00000000..d97f5eb5
--- /dev/null
+++ b/backend/src/interfaces/student-request.ts
@@ -0,0 +1,23 @@
+import { mapToStudentDTO } from './student.js';
+import { ClassJoinRequest } from '../entities/classes/class-join-request.entity.js';
+import { getClassJoinRequestRepository } from '../data/repositories.js';
+import { Student } from '../entities/users/student.entity.js';
+import { Class } from '../entities/classes/class.entity.js';
+import { ClassJoinRequestDTO } from '@dwengo-1/common/interfaces/class-join-request';
+import { ClassJoinRequestStatus } from '@dwengo-1/common/util/class-join-request';
+
+export function mapToStudentRequestDTO(request: ClassJoinRequest): ClassJoinRequestDTO {
+    return {
+        requester: mapToStudentDTO(request.requester),
+        class: request.class.classId!,
+        status: request.status,
+    };
+}
+
+export function mapToStudentRequest(student: Student, cls: Class): ClassJoinRequest {
+    return getClassJoinRequestRepository().create({
+        requester: student,
+        class: cls,
+        status: ClassJoinRequestStatus.Open,
+    });
+}
diff --git a/backend/src/routes/student-join-requests.ts b/backend/src/routes/student-join-requests.ts
new file mode 100644
index 00000000..daf79f09
--- /dev/null
+++ b/backend/src/routes/student-join-requests.ts
@@ -0,0 +1,19 @@
+import express from 'express';
+import {
+    createStudentRequestHandler,
+    deleteClassJoinRequestHandler,
+    getStudentRequestHandler,
+    getStudentRequestsHandler,
+} from '../controllers/students.js';
+
+const router = express.Router({ mergeParams: true });
+
+router.get('/', getStudentRequestsHandler);
+
+router.post('/', createStudentRequestHandler);
+
+router.get('/:classId', getStudentRequestHandler);
+
+router.delete('/:classId', deleteClassJoinRequestHandler);
+
+export default router;
diff --git a/backend/src/routes/students.ts b/backend/src/routes/students.ts
index d58c2adc..0f5d5349 100644
--- a/backend/src/routes/students.ts
+++ b/backend/src/routes/students.ts
@@ -7,8 +7,10 @@ import {
     getStudentClassesHandler,
     getStudentGroupsHandler,
     getStudentHandler,
+    getStudentQuestionsHandler,
     getStudentSubmissionsHandler,
 } from '../controllers/students.js';
+import joinRequestRouter from './student-join-requests.js';
 
 const router = express.Router();
 
@@ -17,30 +19,26 @@ router.get('/', getAllStudentsHandler);
 
 router.post('/', createStudentHandler);
 
-router.delete('/', deleteStudentHandler);
-
 router.delete('/:username', deleteStudentHandler);
 
 // Information about a student's profile
 router.get('/:username', getStudentHandler);
 
 // The list of classes a student is in
-router.get('/:id/classes', getStudentClassesHandler);
+router.get('/:username/classes', getStudentClassesHandler);
 
 // The list of submissions a student has made
-router.get('/:id/submissions', getStudentSubmissionsHandler);
+router.get('/:username/submissions', getStudentSubmissionsHandler);
 
 // The list of assignments a student has
-router.get('/:id/assignments', getStudentAssignmentsHandler);
+router.get('/:username/assignments', getStudentAssignmentsHandler);
 
 // The list of groups a student is in
-router.get('/:id/groups', getStudentGroupsHandler);
+router.get('/:username/groups', getStudentGroupsHandler);
 
 // A list of questions a user has created
-router.get('/:id/questions', (_req, res) => {
-    res.json({
-        questions: ['0'],
-    });
-});
+router.get('/:username/questions', getStudentQuestionsHandler);
+
+router.use('/:username/joinRequests', joinRequestRouter);
 
 export default router;
diff --git a/backend/src/routes/teachers.ts b/backend/src/routes/teachers.ts
index 3782a6ca..a6106a80 100644
--- a/backend/src/routes/teachers.ts
+++ b/backend/src/routes/teachers.ts
@@ -3,10 +3,12 @@ import {
     createTeacherHandler,
     deleteTeacherHandler,
     getAllTeachersHandler,
+    getStudentJoinRequestHandler,
     getTeacherClassHandler,
     getTeacherHandler,
     getTeacherQuestionHandler,
     getTeacherStudentHandler,
+    updateStudentJoinRequestHandler,
 } from '../controllers/teachers.js';
 const router = express.Router();
 
@@ -15,8 +17,6 @@ router.get('/', getAllTeachersHandler);
 
 router.post('/', createTeacherHandler);
 
-router.delete('/', deleteTeacherHandler);
-
 router.get('/:username', getTeacherHandler);
 
 router.delete('/:username', deleteTeacherHandler);
@@ -27,6 +27,10 @@ router.get('/:username/students', getTeacherStudentHandler);
 
 router.get('/:username/questions', getTeacherQuestionHandler);
 
+router.get('/:username/joinRequests/:classId', getStudentJoinRequestHandler);
+
+router.put('/:username/joinRequests/:classId/:studentUsername', updateStudentJoinRequestHandler);
+
 // Invitations to other classes a teacher received
 router.get('/:id/invitations', (_req, res) => {
     res.json({
diff --git a/backend/src/services/classes.ts b/backend/src/services/classes.ts
index fccbbee0..754277cf 100644
--- a/backend/src/services/classes.ts
+++ b/backend/src/services/classes.ts
@@ -3,12 +3,25 @@ import { mapToClassDTO } from '../interfaces/class.js';
 import { mapToStudentDTO } from '../interfaces/student.js';
 import { mapToTeacherInvitationDTO, mapToTeacherInvitationDTOIds } from '../interfaces/teacher-invitation.js';
 import { getLogger } from '../logging/initalize.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
+import { Class } from '../entities/classes/class.entity.js';
 import { ClassDTO } from '@dwengo-1/common/interfaces/class';
 import { TeacherInvitationDTO } from '@dwengo-1/common/interfaces/teacher-invitation';
 import { StudentDTO } from '@dwengo-1/common/interfaces/student';
 
 const logger = getLogger();
 
+export async function fetchClass(classId: string): Promise<Class> {
+    const classRepository = getClassRepository();
+    const cls = await classRepository.findById(classId);
+
+    if (!cls) {
+        throw new NotFoundException('Class with id not found');
+    }
+
+    return cls;
+}
+
 export async function getAllClasses(full: boolean): Promise<ClassDTO[] | string[]> {
     const classRepository = getClassRepository();
     const classes = await classRepository.find({}, { populate: ['students', 'teachers'] });
diff --git a/backend/src/services/questions.ts b/backend/src/services/questions.ts
index f92efae0..319061c5 100644
--- a/backend/src/services/questions.ts
+++ b/backend/src/services/questions.ts
@@ -1,8 +1,8 @@
 import { getAnswerRepository, getQuestionRepository } from '../data/repositories.js';
-import { mapToQuestionDTO, mapToQuestionId } from '../interfaces/question.js';
+import { mapToQuestionDTO, mapToQuestionDTOId } from '../interfaces/question.js';
 import { Question } from '../entities/questions/question.entity.js';
 import { Answer } from '../entities/questions/answer.entity.js';
-import { mapToAnswerDTO, mapToAnswerId } from '../interfaces/answer.js';
+import { mapToAnswerDTO, mapToAnswerDTOId } from '../interfaces/answer.js';
 import { QuestionRepository } from '../data/questions/question-repository.js';
 import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
 import { mapToStudent } from '../interfaces/student.js';
@@ -17,13 +17,11 @@ export async function getAllQuestions(id: LearningObjectIdentifier, full: boolea
         return [];
     }
 
-    const questionsDTO: QuestionDTO[] = questions.map(mapToQuestionDTO);
-
     if (full) {
-        return questionsDTO;
+        return questions.map(mapToQuestionDTO);
     }
 
-    return questionsDTO.map(mapToQuestionId);
+    return questions.map(mapToQuestionDTOId);
 }
 
 async function fetchQuestion(questionId: QuestionId): Promise<Question | null> {
@@ -61,13 +59,11 @@ export async function getAnswersByQuestion(questionId: QuestionId, full: boolean
         return [];
     }
 
-    const answersDTO = answers.map(mapToAnswerDTO);
-
     if (full) {
-        return answersDTO;
+        return answers.map(mapToAnswerDTO);
     }
 
-    return answersDTO.map(mapToAnswerId);
+    return answers.map(mapToAnswerDTOId);
 }
 
 export async function createQuestion(questionDTO: QuestionDTO): Promise<QuestionDTO | null> {
diff --git a/backend/src/services/students.ts b/backend/src/services/students.ts
index 968b556b..dc40e468 100644
--- a/backend/src/services/students.ts
+++ b/backend/src/services/students.ts
@@ -1,67 +1,75 @@
-import { getClassRepository, getGroupRepository, getStudentRepository, getSubmissionRepository } from '../data/repositories.js';
+import {
+    getClassJoinRequestRepository,
+    getClassRepository,
+    getGroupRepository,
+    getQuestionRepository,
+    getStudentRepository,
+    getSubmissionRepository,
+} from '../data/repositories.js';
 import { mapToClassDTO } from '../interfaces/class.js';
 import { mapToGroupDTO, mapToGroupDTOId } from '../interfaces/group.js';
 import { mapToStudent, mapToStudentDTO } from '../interfaces/student.js';
 import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
 import { getAllAssignments } from './assignments.js';
-import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
+import { mapToQuestionDTO, mapToQuestionDTOId } from '../interfaces/question.js';
+import { mapToStudentRequest, mapToStudentRequestDTO } from '../interfaces/student-request.js';
+import { Student } from '../entities/users/student.entity.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
+import { fetchClass } from './classes.js';
+import { StudentDTO } from '@dwengo-1/common/interfaces/student';
 import { ClassDTO } from '@dwengo-1/common/interfaces/class';
+import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
 import { GroupDTO } from '@dwengo-1/common/interfaces/group';
 import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
-import { StudentDTO } from '@dwengo-1/common/interfaces/student';
-import { getLogger } from '../logging/initalize.js';
+import { QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
+import { ClassJoinRequestDTO } from '@dwengo-1/common/interfaces/class-join-request';
 
 export async function getAllStudents(full: boolean): Promise<StudentDTO[] | string[]> {
     const studentRepository = getStudentRepository();
-    const students = await studentRepository.findAll();
+    const users = await studentRepository.findAll();
 
     if (full) {
-        return students.map(mapToStudentDTO);
+        return users.map(mapToStudentDTO);
     }
 
-    return students.map((student) => student.username);
+    return users.map((user) => user.username);
 }
 
-export async function getStudent(username: string): Promise<StudentDTO | null> {
+export async function fetchStudent(username: string): Promise<Student> {
     const studentRepository = getStudentRepository();
     const user = await studentRepository.findByUsername(username);
-    return user ? mapToStudentDTO(user) : null;
+
+    if (!user) {
+        throw new NotFoundException('Student with username not found');
+    }
+
+    return user;
 }
 
-export async function createStudent(userData: StudentDTO): Promise<StudentDTO | null> {
+export async function getStudent(username: string): Promise<StudentDTO> {
+    const user = await fetchStudent(username);
+    return mapToStudentDTO(user);
+}
+
+export async function createStudent(userData: StudentDTO): Promise<StudentDTO> {
     const studentRepository = getStudentRepository();
 
     const newStudent = mapToStudent(userData);
     await studentRepository.save(newStudent, { preventOverwrite: true });
-    return mapToStudentDTO(newStudent);
+    return userData;
 }
 
-export async function deleteStudent(username: string): Promise<StudentDTO | null> {
+export async function deleteStudent(username: string): Promise<StudentDTO> {
     const studentRepository = getStudentRepository();
 
-    const user = await studentRepository.findByUsername(username);
+    const student = await fetchStudent(username); // Throws error if it does not exist
 
-    if (!user) {
-        return null;
-    }
-
-    try {
-        await studentRepository.deleteByUsername(username);
-
-        return mapToStudentDTO(user);
-    } catch (e) {
-        getLogger().error(e);
-        return null;
-    }
+    await studentRepository.deleteByUsername(username);
+    return mapToStudentDTO(student);
 }
 
 export async function getStudentClasses(username: string, full: boolean): Promise<ClassDTO[] | string[]> {
-    const studentRepository = getStudentRepository();
-    const student = await studentRepository.findByUsername(username);
-
-    if (!student) {
-        return [];
-    }
+    const student = await fetchStudent(username);
 
     const classRepository = getClassRepository();
     const classes = await classRepository.findByStudent(student);
@@ -74,12 +82,7 @@ export async function getStudentClasses(username: string, full: boolean): Promis
 }
 
 export async function getStudentAssignments(username: string, full: boolean): Promise<AssignmentDTO[]> {
-    const studentRepository = getStudentRepository();
-    const student = await studentRepository.findByUsername(username);
-
-    if (!student) {
-        return [];
-    }
+    const student = await fetchStudent(username);
 
     const classRepository = getClassRepository();
     const classes = await classRepository.findByStudent(student);
@@ -88,12 +91,7 @@ export async function getStudentAssignments(username: string, full: boolean): Pr
 }
 
 export async function getStudentGroups(username: string, full: boolean): Promise<GroupDTO[]> {
-    const studentRepository = getStudentRepository();
-    const student = await studentRepository.findByUsername(username);
-
-    if (!student) {
-        return [];
-    }
+    const student = await fetchStudent(username);
 
     const groupRepository = getGroupRepository();
     const groups = await groupRepository.findAllGroupsWithStudent(student);
@@ -106,12 +104,7 @@ export async function getStudentGroups(username: string, full: boolean): Promise
 }
 
 export async function getStudentSubmissions(username: string, full: boolean): Promise<SubmissionDTO[] | SubmissionDTOId[]> {
-    const studentRepository = getStudentRepository();
-    const student = await studentRepository.findByUsername(username);
-
-    if (!student) {
-        return [];
-    }
+    const student = await fetchStudent(username);
 
     const submissionRepository = getSubmissionRepository();
     const submissions = await submissionRepository.findAllSubmissionsForStudent(student);
@@ -122,3 +115,66 @@ export async function getStudentSubmissions(username: string, full: boolean): Pr
 
     return submissions.map(mapToSubmissionDTOId);
 }
+
+export async function getStudentQuestions(username: string, full: boolean): Promise<QuestionDTO[] | QuestionId[]> {
+    const student = await fetchStudent(username);
+
+    const questionRepository = getQuestionRepository();
+    const questions = await questionRepository.findAllByAuthor(student);
+
+    if (full) {
+        return questions.map(mapToQuestionDTO);
+    }
+
+    return questions.map(mapToQuestionDTOId);
+}
+
+export async function createClassJoinRequest(username: string, classId: string): Promise<ClassJoinRequestDTO> {
+    const requestRepo = getClassJoinRequestRepository();
+
+    const student = await fetchStudent(username); // Throws error if student not found
+    const cls = await fetchClass(classId);
+
+    const request = mapToStudentRequest(student, cls);
+    await requestRepo.save(request, { preventOverwrite: true });
+    return mapToStudentRequestDTO(request);
+}
+
+export async function getJoinRequestsByStudent(username: string): Promise<ClassJoinRequestDTO[]> {
+    const requestRepo = getClassJoinRequestRepository();
+
+    const student = await fetchStudent(username);
+
+    const requests = await requestRepo.findAllRequestsBy(student);
+    return requests.map(mapToStudentRequestDTO);
+}
+
+export async function getJoinRequestByStudentClass(username: string, classId: string): Promise<ClassJoinRequestDTO> {
+    const requestRepo = getClassJoinRequestRepository();
+
+    const student = await fetchStudent(username);
+    const cls = await fetchClass(classId);
+
+    const request = await requestRepo.findByStudentAndClass(student, cls);
+    if (!request) {
+        throw new NotFoundException('Join request not found');
+    }
+
+    return mapToStudentRequestDTO(request);
+}
+
+export async function deleteClassJoinRequest(username: string, classId: string): Promise<ClassJoinRequestDTO> {
+    const requestRepo = getClassJoinRequestRepository();
+
+    const student = await fetchStudent(username);
+    const cls = await fetchClass(classId);
+
+    const request = await requestRepo.findByStudentAndClass(student, cls);
+
+    if (!request) {
+        throw new NotFoundException('Join request not found');
+    }
+
+    await requestRepo.deleteBy(student, cls);
+    return mapToStudentRequestDTO(request);
+}
diff --git a/backend/src/services/teachers.ts b/backend/src/services/teachers.ts
index 3986462b..1b7643fb 100644
--- a/backend/src/services/teachers.ts
+++ b/backend/src/services/teachers.ts
@@ -1,137 +1,165 @@
-import { getClassRepository, getLearningObjectRepository, getQuestionRepository, getTeacherRepository } from '../data/repositories.js';
+import {
+    getClassJoinRequestRepository,
+    getClassRepository,
+    getLearningObjectRepository,
+    getQuestionRepository,
+    getTeacherRepository,
+} from '../data/repositories.js';
 import { mapToClassDTO } from '../interfaces/class.js';
-import { getClassStudents } from './classes.js';
-import { mapToQuestionDTO, mapToQuestionId } from '../interfaces/question.js';
+import { mapToQuestionDTO, mapToQuestionDTOId } from '../interfaces/question.js';
 import { mapToTeacher, mapToTeacherDTO } from '../interfaces/teacher.js';
-import { ClassDTO } from '@dwengo-1/common/interfaces/class';
+import { Teacher } from '../entities/users/teacher.entity.js';
+import { fetchStudent } from './students.js';
+import { ClassJoinRequest } from '../entities/classes/class-join-request.entity.js';
+import { mapToStudentRequestDTO } from '../interfaces/student-request.js';
+import { TeacherRepository } from '../data/users/teacher-repository.js';
+import { ClassRepository } from '../data/classes/class-repository.js';
+import { Class } from '../entities/classes/class.entity.js';
+import { LearningObjectRepository } from '../data/content/learning-object-repository.js';
+import { LearningObject } from '../entities/content/learning-object.entity.js';
+import { QuestionRepository } from '../data/questions/question-repository.js';
+import { Question } from '../entities/questions/question.entity.js';
+import { ClassJoinRequestRepository } from '../data/classes/class-join-request-repository.js';
+import { Student } from '../entities/users/student.entity.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
+import { getClassStudents } from './classes.js';
 import { TeacherDTO } from '@dwengo-1/common/interfaces/teacher';
+import { ClassDTO } from '@dwengo-1/common/interfaces/class';
 import { StudentDTO } from '@dwengo-1/common/interfaces/student';
 import { QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
-import { getLogger } from '../logging/initalize.js';
+import { ClassJoinRequestDTO } from '@dwengo-1/common/interfaces/class-join-request';
+import { ClassJoinRequestStatus } from '@dwengo-1/common/util/class-join-request';
 
 export async function getAllTeachers(full: boolean): Promise<TeacherDTO[] | string[]> {
-    const teacherRepository = getTeacherRepository();
-    const teachers = await teacherRepository.findAll();
+    const teacherRepository: TeacherRepository = getTeacherRepository();
+    const users: Teacher[] = await teacherRepository.findAll();
 
     if (full) {
-        return teachers.map(mapToTeacherDTO);
+        return users.map(mapToTeacherDTO);
+    }
+    return users.map((user) => user.username);
+}
+
+export async function fetchTeacher(username: string): Promise<Teacher> {
+    const teacherRepository: TeacherRepository = getTeacherRepository();
+    const user: Teacher | null = await teacherRepository.findByUsername(username);
+
+    if (!user) {
+        throw new NotFoundException('Teacher with username not found');
     }
 
-    return teachers.map((teacher) => teacher.username);
+    return user;
 }
 
-export async function getTeacher(username: string): Promise<TeacherDTO | null> {
-    const teacherRepository = getTeacherRepository();
-    const user = await teacherRepository.findByUsername(username);
-    return user ? mapToTeacherDTO(user) : null;
+export async function getTeacher(username: string): Promise<TeacherDTO> {
+    const user: Teacher = await fetchTeacher(username);
+    return mapToTeacherDTO(user);
 }
 
-export async function createTeacher(userData: TeacherDTO): Promise<TeacherDTO | null> {
-    const teacherRepository = getTeacherRepository();
+export async function createTeacher(userData: TeacherDTO): Promise<TeacherDTO> {
+    const teacherRepository: TeacherRepository = getTeacherRepository();
 
     const newTeacher = mapToTeacher(userData);
     await teacherRepository.save(newTeacher, { preventOverwrite: true });
-
     return mapToTeacherDTO(newTeacher);
 }
 
-export async function deleteTeacher(username: string): Promise<TeacherDTO | null> {
-    const teacherRepository = getTeacherRepository();
+export async function deleteTeacher(username: string): Promise<TeacherDTO> {
+    const teacherRepository: TeacherRepository = getTeacherRepository();
 
-    const user = await teacherRepository.findByUsername(username);
+    const teacher = await fetchTeacher(username); // Throws error if it does not exist
 
-    if (!user) {
-        return null;
-    }
-
-    try {
-        await teacherRepository.deleteByUsername(username);
-
-        return mapToTeacherDTO(user);
-    } catch (e) {
-        getLogger().error(e);
-        return null;
-    }
+    await teacherRepository.deleteByUsername(username);
+    return mapToTeacherDTO(teacher);
 }
 
-export async function fetchClassesByTeacher(username: string): Promise<ClassDTO[] | null> {
-    const teacherRepository = getTeacherRepository();
-    const teacher = await teacherRepository.findByUsername(username);
-    if (!teacher) {
-        return null;
-    }
+async function fetchClassesByTeacher(username: string): Promise<ClassDTO[]> {
+    const teacher: Teacher = await fetchTeacher(username);
 
-    const classRepository = getClassRepository();
-    const classes = await classRepository.findByTeacher(teacher);
+    const classRepository: ClassRepository = getClassRepository();
+    const classes: Class[] = await classRepository.findByTeacher(teacher);
     return classes.map(mapToClassDTO);
 }
 
-export async function getClassesByTeacher(username: string, full: boolean): Promise<ClassDTO[] | string[] | null> {
-    const classes = await fetchClassesByTeacher(username);
-
-    if (!classes) {
-        return null;
-    }
+export async function getClassesByTeacher(username: string, full: boolean): Promise<ClassDTO[] | string[]> {
+    const classes: ClassDTO[] = await fetchClassesByTeacher(username);
 
     if (full) {
         return classes;
     }
-
     return classes.map((cls) => cls.id);
 }
 
-export async function fetchStudentsByTeacher(username: string): Promise<StudentDTO[] | null> {
-    const classes = (await getClassesByTeacher(username, false)) as string[];
+export async function getStudentsByTeacher(username: string, full: boolean): Promise<StudentDTO[] | string[]> {
+    const classes: ClassDTO[] = await fetchClassesByTeacher(username);
 
-    if (!classes) {
-        return null;
+    if (!classes || classes.length === 0) {
+        return [];
     }
 
-    return (await Promise.all(classes.map(async (id) => getClassStudents(id)))).flat();
-}
-
-export async function getStudentsByTeacher(username: string, full: boolean): Promise<StudentDTO[] | string[] | null> {
-    const students = await fetchStudentsByTeacher(username);
-
-    if (!students) {
-        return null;
-    }
+    const classIds: string[] = classes.map((cls) => cls.id);
 
+    const students: StudentDTO[] = (await Promise.all(classIds.map(async (id) => getClassStudents(id)))).flat();
     if (full) {
         return students;
     }
-
     return students.map((student) => student.username);
 }
 
-export async function fetchTeacherQuestions(username: string): Promise<QuestionDTO[] | null> {
-    const teacherRepository = getTeacherRepository();
-    const teacher = await teacherRepository.findByUsername(username);
-    if (!teacher) {
-        return null;
-    }
+export async function getTeacherQuestions(username: string, full: boolean): Promise<QuestionDTO[] | QuestionId[]> {
+    const teacher: Teacher = await fetchTeacher(username);
 
     // Find all learning objects that this teacher manages
-    const learningObjectRepository = getLearningObjectRepository();
-    const learningObjects = await learningObjectRepository.findAllByTeacher(teacher);
+    const learningObjectRepository: LearningObjectRepository = getLearningObjectRepository();
+    const learningObjects: LearningObject[] = await learningObjectRepository.findAllByTeacher(teacher);
+
+    if (!learningObjects || learningObjects.length === 0) {
+        return [];
+    }
 
     // Fetch all questions related to these learning objects
-    const questionRepository = getQuestionRepository();
-    const questions = await questionRepository.findAllByLearningObjects(learningObjects);
-
-    return questions.map(mapToQuestionDTO);
-}
-
-export async function getQuestionsByTeacher(username: string, full: boolean): Promise<QuestionDTO[] | QuestionId[] | null> {
-    const questions = await fetchTeacherQuestions(username);
-
-    if (!questions) {
-        return null;
-    }
+    const questionRepository: QuestionRepository = getQuestionRepository();
+    const questions: Question[] = await questionRepository.findAllByLearningObjects(learningObjects);
 
     if (full) {
-        return questions;
+        return questions.map(mapToQuestionDTO);
     }
 
-    return questions.map(mapToQuestionId);
+    return questions.map(mapToQuestionDTOId);
+}
+
+export async function getJoinRequestsByClass(classId: string): Promise<ClassJoinRequestDTO[]> {
+    const classRepository: ClassRepository = getClassRepository();
+    const cls: Class | null = await classRepository.findById(classId);
+
+    if (!cls) {
+        throw new NotFoundException('Class with id not found');
+    }
+
+    const requestRepo: ClassJoinRequestRepository = getClassJoinRequestRepository();
+    const requests: ClassJoinRequest[] = await requestRepo.findAllOpenRequestsTo(cls);
+    return requests.map(mapToStudentRequestDTO);
+}
+
+export async function updateClassJoinRequestStatus(studentUsername: string, classId: string, accepted = true): Promise<ClassJoinRequestDTO> {
+    const requestRepo: ClassJoinRequestRepository = getClassJoinRequestRepository();
+    const classRepo: ClassRepository = getClassRepository();
+
+    const student: Student = await fetchStudent(studentUsername);
+    const cls: Class | null = await classRepo.findById(classId);
+
+    if (!cls) {
+        throw new NotFoundException('Class not found');
+    }
+
+    const request: ClassJoinRequest | null = await requestRepo.findByStudentAndClass(student, cls);
+
+    if (!request) {
+        throw new NotFoundException('Join request not found');
+    }
+
+    request.status = accepted ? ClassJoinRequestStatus.Accepted : ClassJoinRequestStatus.Declined;
+
+    await requestRepo.save(request);
+    return mapToStudentRequestDTO(request);
 }
diff --git a/backend/tests/controllers/students.test.ts b/backend/tests/controllers/students.test.ts
new file mode 100644
index 00000000..93f35c48
--- /dev/null
+++ b/backend/tests/controllers/students.test.ts
@@ -0,0 +1,232 @@
+import { setupTestApp } from '../setup-tests.js';
+import { describe, it, expect, beforeAll, beforeEach, vi, Mock } from 'vitest';
+import { Request, Response } from 'express';
+import {
+    getAllStudentsHandler,
+    getStudentHandler,
+    createStudentHandler,
+    deleteStudentHandler,
+    getStudentClassesHandler,
+    getStudentGroupsHandler,
+    getStudentSubmissionsHandler,
+    getStudentQuestionsHandler,
+    createStudentRequestHandler,
+    getStudentRequestsHandler,
+    deleteClassJoinRequestHandler,
+    getStudentRequestHandler,
+} from '../../src/controllers/students.js';
+import { TEST_STUDENTS } from '../test_assets/users/students.testdata.js';
+import { NotFoundException } from '../../src/exceptions/not-found-exception.js';
+import { BadRequestException } from '../../src/exceptions/bad-request-exception.js';
+import { ConflictException } from '../../src/exceptions/conflict-exception.js';
+import { EntityAlreadyExistsException } from '../../src/exceptions/entity-already-exists-exception.js';
+import { StudentDTO } from '@dwengo-1/common/interfaces/student';
+
+describe('Student controllers', () => {
+    let req: Partial<Request>;
+    let res: Partial<Response>;
+
+    let jsonMock: Mock;
+
+    beforeAll(async () => {
+        await setupTestApp();
+    });
+
+    beforeEach(() => {
+        jsonMock = vi.fn();
+        res = {
+            json: jsonMock,
+        };
+    });
+
+    it('Get student', async () => {
+        req = { params: { username: 'DireStraits' } };
+
+        await getStudentHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ student: expect.anything() }));
+    });
+
+    it('Student not found', async () => {
+        req = { params: { username: 'doesnotexist' } };
+
+        await expect(async () => getStudentHandler(req as Request, res as Response)).rejects.toThrow(NotFoundException);
+    });
+
+    it('No username', async () => {
+        req = { params: {} };
+
+        await expect(async () => getStudentHandler(req as Request, res as Response)).rejects.toThrowError(BadRequestException);
+    });
+
+    it('Create and delete student', async () => {
+        const student = {
+            id: 'coolstudent',
+            username: 'coolstudent',
+            firstName: 'New',
+            lastName: 'Student',
+        } as StudentDTO;
+        req = {
+            body: student,
+        };
+
+        await createStudentHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ student: expect.objectContaining(student) }));
+
+        req = { params: { username: 'coolstudent' } };
+
+        await deleteStudentHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ student: expect.objectContaining(student) }));
+    });
+
+    it('Create duplicate student', async () => {
+        req = {
+            body: {
+                username: 'DireStraits',
+                firstName: 'dupe',
+                lastName: 'dupe',
+            },
+        };
+
+        await expect(async () => createStudentHandler(req as Request, res as Response)).rejects.toThrowError(EntityAlreadyExistsException);
+    });
+
+    it('Create student no body', async () => {
+        req = { body: {} };
+
+        await expect(async () => createStudentHandler(req as Request, res as Response)).rejects.toThrowError(BadRequestException);
+    });
+
+    it('Student list', async () => {
+        req = { query: { full: 'true' } };
+
+        await getAllStudentsHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ students: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+
+        // Check is DireStraits is part of the student list
+        const studentUsernames = result.students.map((s: StudentDTO) => s.username);
+        expect(studentUsernames).toContain('DireStraits');
+
+        // Check length, +1 because of create
+        expect(result.students).toHaveLength(TEST_STUDENTS.length);
+    });
+
+    it('Student classes', async () => {
+        req = { params: { username: 'DireStraits' }, query: {} };
+
+        await getStudentClassesHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ classes: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+        expect(result.classes).to.have.length.greaterThan(0);
+    });
+
+    it('Student groups', async () => {
+        req = { params: { username: 'DireStraits' }, query: {} };
+
+        await getStudentGroupsHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ groups: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+        expect(result.groups).to.have.length.greaterThan(0);
+    });
+
+    it('Student submissions', async () => {
+        req = { params: { username: 'DireStraits' }, query: { full: 'true' } };
+
+        await getStudentSubmissionsHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ submissions: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+        expect(result.submissions).to.have.length.greaterThan(0);
+    });
+
+    it('Student questions', async () => {
+        req = { params: { username: 'DireStraits' }, query: { full: 'true' } };
+
+        await getStudentQuestionsHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ questions: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+        expect(result.questions).to.have.length.greaterThan(0);
+    });
+
+    it('Deleting non-existent student', async () => {
+        req = { params: { username: 'doesnotexist' } };
+
+        await expect(async () => deleteStudentHandler(req as Request, res as Response)).rejects.toThrow(NotFoundException);
+    });
+
+    it('Get join requests by student', async () => {
+        req = {
+            params: { username: 'PinkFloyd' },
+        };
+
+        await getStudentRequestsHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(
+            expect.objectContaining({
+                requests: expect.anything(),
+            })
+        );
+
+        const result = jsonMock.mock.lastCall?.[0];
+        // Console.log('[JOIN REQUESTS]', result.requests);
+        expect(result.requests.length).toBeGreaterThan(0);
+    });
+
+    it('Get join request by student and class', async () => {
+        req = {
+            params: { username: 'PinkFloyd', classId: 'id02' },
+        };
+
+        await getStudentRequestHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(
+            expect.objectContaining({
+                request: expect.anything(),
+            })
+        );
+    });
+
+    it('Create join request', async () => {
+        req = {
+            params: { username: 'Noordkaap' },
+            body: { classId: 'id02' },
+        };
+
+        await createStudentRequestHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ request: expect.anything() }));
+    });
+
+    it('Create join request duplicate', async () => {
+        req = {
+            params: { username: 'Tool' },
+            body: { classId: 'id02' },
+        };
+
+        await expect(async () => createStudentRequestHandler(req as Request, res as Response)).rejects.toThrow(ConflictException);
+    });
+
+    it('Delete join request', async () => {
+        req = {
+            params: { username: 'Noordkaap', classId: 'id02' },
+        };
+
+        await deleteClassJoinRequestHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ request: expect.anything() }));
+
+        await expect(async () => deleteClassJoinRequestHandler(req as Request, res as Response)).rejects.toThrow(NotFoundException);
+    });
+});
diff --git a/backend/tests/controllers/teachers.test.ts b/backend/tests/controllers/teachers.test.ts
new file mode 100644
index 00000000..bee23987
--- /dev/null
+++ b/backend/tests/controllers/teachers.test.ts
@@ -0,0 +1,204 @@
+import { beforeAll, beforeEach, describe, expect, it, Mock, vi } from 'vitest';
+import { Request, Response } from 'express';
+import { setupTestApp } from '../setup-tests.js';
+import { NotFoundException } from '../../src/exceptions/not-found-exception.js';
+import {
+    createTeacherHandler,
+    deleteTeacherHandler,
+    getAllTeachersHandler,
+    getStudentJoinRequestHandler,
+    getTeacherClassHandler,
+    getTeacherHandler,
+    getTeacherStudentHandler,
+    updateStudentJoinRequestHandler,
+} from '../../src/controllers/teachers.js';
+import { BadRequestException } from '../../src/exceptions/bad-request-exception.js';
+import { EntityAlreadyExistsException } from '../../src/exceptions/entity-already-exists-exception.js';
+import { getStudentRequestsHandler } from '../../src/controllers/students.js';
+import { TeacherDTO } from '@dwengo-1/common/interfaces/teacher';
+
+describe('Teacher controllers', () => {
+    let req: Partial<Request>;
+    let res: Partial<Response>;
+
+    let jsonMock: Mock;
+
+    beforeAll(async () => {
+        await setupTestApp();
+    });
+
+    beforeEach(() => {
+        jsonMock = vi.fn();
+        res = {
+            json: jsonMock,
+        };
+    });
+
+    it('Get teacher', async () => {
+        req = { params: { username: 'FooFighters' } };
+
+        await getTeacherHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ teacher: expect.anything() }));
+    });
+
+    it('Teacher not found', async () => {
+        req = { params: { username: 'doesnotexist' } };
+
+        await expect(async () => getTeacherHandler(req as Request, res as Response)).rejects.toThrow(NotFoundException);
+    });
+
+    it('No username', async () => {
+        req = { params: {} };
+
+        await expect(async () => getTeacherHandler(req as Request, res as Response)).rejects.toThrowError(BadRequestException);
+    });
+
+    it('Create and delete teacher', async () => {
+        const teacher = {
+            id: 'coolteacher',
+            username: 'coolteacher',
+            firstName: 'New',
+            lastName: 'Teacher',
+        };
+        req = {
+            body: teacher,
+        };
+
+        await createTeacherHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ teacher: expect.objectContaining(teacher) }));
+
+        req = { params: { username: 'coolteacher' } };
+
+        await deleteTeacherHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ teacher: expect.objectContaining(teacher) }));
+    });
+
+    it('Create duplicate student', async () => {
+        req = {
+            body: {
+                username: 'FooFighters',
+                firstName: 'Dave',
+                lastName: 'Grohl',
+            },
+        };
+
+        await expect(async () => createTeacherHandler(req as Request, res as Response)).rejects.toThrowError(EntityAlreadyExistsException);
+    });
+
+    it('Create teacher no body', async () => {
+        req = { body: {} };
+
+        await expect(async () => createTeacherHandler(req as Request, res as Response)).rejects.toThrowError(BadRequestException);
+    });
+
+    it('Teacher list', async () => {
+        req = { query: { full: 'true' } };
+
+        await getAllTeachersHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ teachers: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+
+        const teacherUsernames = result.teachers.map((s: TeacherDTO) => s.username);
+        expect(teacherUsernames).toContain('FooFighters');
+
+        expect(result.teachers).toHaveLength(4);
+    });
+
+    it('Deleting non-existent student', async () => {
+        req = { params: { username: 'doesnotexist' } };
+
+        await expect(async () => deleteTeacherHandler(req as Request, res as Response)).rejects.toThrow(NotFoundException);
+    });
+
+    it('Get teacher classes', async () => {
+        req = {
+            params: { username: 'FooFighters' },
+            query: { full: 'true' },
+        };
+
+        await getTeacherClassHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ classes: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+        // Console.log('[TEACHER CLASSES]', result);
+        expect(result.classes.length).toBeGreaterThan(0);
+    });
+
+    it('Get teacher students', async () => {
+        req = {
+            params: { username: 'FooFighters' },
+            query: { full: 'true' },
+        };
+
+        await getTeacherStudentHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ students: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+        // Console.log('[TEACHER STUDENTS]', result.students);
+        expect(result.students.length).toBeGreaterThan(0);
+    });
+
+    /*
+
+    It('Get teacher questions', async () => {
+        req = {
+            params: { username: 'FooFighters' },
+            query: { full: 'true' },
+        };
+
+        await getTeacherQuestionHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ questions: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+        // console.log('[TEACHER QUESTIONS]', result.questions);
+        expect(result.questions.length).toBeGreaterThan(0);
+
+        // TODO fix
+    });
+
+     */
+
+    it('Get join requests by class', async () => {
+        req = {
+            query: { username: 'LimpBizkit' },
+            params: { classId: 'id02' },
+        };
+
+        await getStudentJoinRequestHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ joinRequests: expect.anything() }));
+
+        const result = jsonMock.mock.lastCall?.[0];
+        // Console.log('[JOIN REQUESTS FOR CLASS]', result.joinRequests);
+        expect(result.joinRequests.length).toBeGreaterThan(0);
+    });
+
+    it('Update join request status', async () => {
+        req = {
+            query: { username: 'LimpBizkit', studentUsername: 'PinkFloyd' },
+            params: { classId: 'id02' },
+            body: { accepted: 'true' },
+        };
+
+        await updateStudentJoinRequestHandler(req as Request, res as Response);
+
+        expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ request: expect.anything() }));
+
+        req = {
+            params: { username: 'PinkFloyd' },
+        };
+
+        await getStudentRequestsHandler(req as Request, res as Response);
+
+        const status: boolean = jsonMock.mock.lastCall?.[0].requests[0].status;
+        expect(status).toBeTruthy();
+    });
+});
diff --git a/backend/tests/test_assets/users/students.testdata.ts b/backend/tests/test_assets/users/students.testdata.ts
index 7d69db9e..5cd75787 100644
--- a/backend/tests/test_assets/users/students.testdata.ts
+++ b/backend/tests/test_assets/users/students.testdata.ts
@@ -1,49 +1,19 @@
 import { EntityManager } from '@mikro-orm/core';
 import { Student } from '../../../src/entities/users/student.entity';
 
+// 🔓 Ruwe testdata array — herbruikbaar in assertions
+export const TEST_STUDENTS = [
+    { username: 'Noordkaap', firstName: 'Stijn', lastName: 'Meuris' },
+    { username: 'DireStraits', firstName: 'Mark', lastName: 'Knopfler' },
+    { username: 'Tool', firstName: 'Maynard', lastName: 'Keenan' },
+    { username: 'SmashingPumpkins', firstName: 'Billy', lastName: 'Corgan' },
+    { username: 'PinkFloyd', firstName: 'David', lastName: 'Gilmoure' },
+    { username: 'TheDoors', firstName: 'Jim', lastName: 'Morisson' },
+    // ⚠️ Deze mag niet gebruikt worden in elke test!
+    { username: 'Nirvana', firstName: 'Kurt', lastName: 'Cobain' },
+];
+
+// 🏗️ Functie die ORM entities maakt uit de data array
 export function makeTestStudents(em: EntityManager): Student[] {
-    const student01 = em.create(Student, {
-        username: 'Noordkaap',
-        firstName: 'Stijn',
-        lastName: 'Meuris',
-    });
-
-    const student02 = em.create(Student, {
-        username: 'DireStraits',
-        firstName: 'Mark',
-        lastName: 'Knopfler',
-    });
-
-    const student03 = em.create(Student, {
-        username: 'Tool',
-        firstName: 'Maynard',
-        lastName: 'Keenan',
-    });
-
-    const student04 = em.create(Student, {
-        username: 'SmashingPumpkins',
-        firstName: 'Billy',
-        lastName: 'Corgan',
-    });
-
-    const student05 = em.create(Student, {
-        username: 'PinkFloyd',
-        firstName: 'David',
-        lastName: 'Gilmoure',
-    });
-
-    const student06 = em.create(Student, {
-        username: 'TheDoors',
-        firstName: 'Jim',
-        lastName: 'Morisson',
-    });
-
-    // Do not use for any tests, gets deleted in a unit test
-    const student07 = em.create(Student, {
-        username: 'Nirvana',
-        firstName: 'Kurt',
-        lastName: 'Cobain',
-    });
-
-    return [student01, student02, student03, student04, student05, student06, student07];
+    return TEST_STUDENTS.map((data) => em.create(Student, data));
 }
diff --git a/common/src/interfaces/class-join-request.ts b/common/src/interfaces/class-join-request.ts
new file mode 100644
index 00000000..6787998b
--- /dev/null
+++ b/common/src/interfaces/class-join-request.ts
@@ -0,0 +1,8 @@
+import { StudentDTO } from './student';
+import { ClassJoinRequestStatus } from '../util/class-join-request';
+
+export interface ClassJoinRequestDTO {
+    requester: StudentDTO;
+    class: string;
+    status: ClassJoinRequestStatus;
+}
diff --git a/common/src/interfaces/theme.ts b/common/src/interfaces/theme.ts
new file mode 100644
index 00000000..5334b775
--- /dev/null
+++ b/common/src/interfaces/theme.ts
@@ -0,0 +1,4 @@
+export interface Theme {
+    title: string;
+    hruids: string[];
+}
diff --git a/frontend/src/controllers/assignments.ts b/frontend/src/controllers/assignments.ts
new file mode 100644
index 00000000..5fd5090a
--- /dev/null
+++ b/frontend/src/controllers/assignments.ts
@@ -0,0 +1,5 @@
+import type { AssignmentDTO } from "@dwengo-1/interfaces/assignment";
+
+export interface AssignmentsResponse {
+    assignments: AssignmentDTO[];
+} // TODO ID
diff --git a/frontend/src/controllers/classes.ts b/frontend/src/controllers/classes.ts
new file mode 100644
index 00000000..d2d95ed5
--- /dev/null
+++ b/frontend/src/controllers/classes.ts
@@ -0,0 +1,5 @@
+import type { ClassDTO } from "@dwengo-1/interfaces/class";
+
+export interface ClassesResponse {
+    classes: ClassDTO[] | string[];
+}
diff --git a/frontend/src/controllers/groups.ts b/frontend/src/controllers/groups.ts
new file mode 100644
index 00000000..d6738e04
--- /dev/null
+++ b/frontend/src/controllers/groups.ts
@@ -0,0 +1,5 @@
+import type { GroupDTO } from "@dwengo-1/interfaces/group";
+
+export interface GroupsResponse {
+    groups: GroupDTO[];
+} // | TODO id
diff --git a/frontend/src/controllers/questions.ts b/frontend/src/controllers/questions.ts
new file mode 100644
index 00000000..9b0182de
--- /dev/null
+++ b/frontend/src/controllers/questions.ts
@@ -0,0 +1,5 @@
+import type { QuestionDTO, QuestionId } from "@dwengo-1/interfaces/question";
+
+export interface QuestionsResponse {
+    questions: QuestionDTO[] | QuestionId[];
+}
diff --git a/frontend/src/controllers/students.ts b/frontend/src/controllers/students.ts
new file mode 100644
index 00000000..b36f1d5a
--- /dev/null
+++ b/frontend/src/controllers/students.ts
@@ -0,0 +1,79 @@
+import { BaseController } from "@/controllers/base-controller.ts";
+import type { ClassesResponse } from "@/controllers/classes.ts";
+import type { AssignmentsResponse } from "@/controllers/assignments.ts";
+import type { GroupsResponse } from "@/controllers/groups.ts";
+import type { SubmissionsResponse } from "@/controllers/submissions.ts";
+import type { QuestionsResponse } from "@/controllers/questions.ts";
+import type { StudentDTO } from "@dwengo-1/interfaces/student";
+import type { ClassJoinRequestDTO } from "@dwengo-1/interfaces/class-join-request";
+
+export interface StudentsResponse {
+    students: StudentDTO[] | string[];
+}
+export interface StudentResponse {
+    student: StudentDTO;
+}
+export interface JoinRequestsResponse {
+    requests: ClassJoinRequestDTO[];
+}
+export interface JoinRequestResponse {
+    request: ClassJoinRequestDTO;
+}
+
+export class StudentController extends BaseController {
+    constructor() {
+        super("student");
+    }
+
+    async getAll(full = true): Promise<StudentsResponse> {
+        return this.get<StudentsResponse>("/", { full });
+    }
+
+    async getByUsername(username: string): Promise<StudentResponse> {
+        return this.get<StudentResponse>(`/${username}`);
+    }
+
+    async createStudent(data: StudentDTO): Promise<StudentResponse> {
+        return this.post<StudentResponse>("/", data);
+    }
+
+    async deleteStudent(username: string): Promise<StudentResponse> {
+        return this.delete<StudentResponse>(`/${username}`);
+    }
+
+    async getClasses(username: string, full = true): Promise<ClassesResponse> {
+        return this.get<ClassesResponse>(`/${username}/classes`, { full });
+    }
+
+    async getAssignments(username: string, full = true): Promise<AssignmentsResponse> {
+        return this.get<AssignmentsResponse>(`/${username}/assignments`, { full });
+    }
+
+    async getGroups(username: string, full = true): Promise<GroupsResponse> {
+        return this.get<GroupsResponse>(`/${username}/groups`, { full });
+    }
+
+    async getSubmissions(username: string): Promise<SubmissionsResponse> {
+        return this.get<SubmissionsResponse>(`/${username}/submissions`);
+    }
+
+    async getQuestions(username: string, full = true): Promise<QuestionsResponse> {
+        return this.get<QuestionsResponse>(`/${username}/questions`, { full });
+    }
+
+    async getJoinRequests(username: string): Promise<JoinRequestsResponse> {
+        return this.get<JoinRequestsResponse>(`/${username}/joinRequests`);
+    }
+
+    async getJoinRequest(username: string, classId: string): Promise<JoinRequestResponse> {
+        return this.get<JoinRequestResponse>(`/${username}/joinRequests/${classId}`);
+    }
+
+    async createJoinRequest(username: string, classId: string): Promise<JoinRequestResponse> {
+        return this.post<JoinRequestResponse>(`/${username}/joinRequests}`, classId);
+    }
+
+    async deleteJoinRequest(username: string, classId: string): Promise<JoinRequestResponse> {
+        return this.delete<JoinRequestResponse>(`/${username}/joinRequests/${classId}`);
+    }
+}
diff --git a/frontend/src/controllers/submissions.ts b/frontend/src/controllers/submissions.ts
new file mode 100644
index 00000000..99b6ba8d
--- /dev/null
+++ b/frontend/src/controllers/submissions.ts
@@ -0,0 +1,5 @@
+import { type SubmissionDTO, SubmissionDTOId } from "@dwengo-1/interfaces/submission";
+
+export interface SubmissionsResponse {
+    submissions: SubmissionDTO[] | SubmissionDTOId[];
+}
diff --git a/frontend/src/controllers/teachers.ts b/frontend/src/controllers/teachers.ts
new file mode 100644
index 00000000..e0d38a6c
--- /dev/null
+++ b/frontend/src/controllers/teachers.ts
@@ -0,0 +1,64 @@
+import { BaseController } from "@/controllers/base-controller.ts";
+import type { JoinRequestResponse, JoinRequestsResponse, StudentsResponse } from "@/controllers/students.ts";
+import type { QuestionsResponse } from "@/controllers/questions.ts";
+import type { ClassesResponse } from "@/controllers/classes.ts";
+import type { TeacherDTO } from "@dwengo-1/interfaces/teacher";
+
+export interface TeachersResponse {
+    teachers: TeacherDTO[] | string[];
+}
+export interface TeacherResponse {
+    teacher: TeacherDTO;
+}
+
+export class TeacherController extends BaseController {
+    constructor() {
+        super("teacher");
+    }
+
+    async getAll(full = false): Promise<TeachersResponse> {
+        return this.get<TeachersResponse>("/", { full });
+    }
+
+    async getByUsername(username: string): Promise<TeacherResponse> {
+        return this.get<TeacherResponse>(`/${username}`);
+    }
+
+    async createTeacher(data: TeacherDTO): Promise<TeacherResponse> {
+        return this.post<TeacherResponse>("/", data);
+    }
+
+    async deleteTeacher(username: string): Promise<TeacherResponse> {
+        return this.delete<TeacherResponse>(`/${username}`);
+    }
+
+    async getClasses(username: string, full = false): Promise<ClassesResponse> {
+        return this.get<ClassesResponse>(`/${username}/classes`, { full });
+    }
+
+    async getStudents(username: string, full = false): Promise<StudentsResponse> {
+        return this.get<StudentsResponse>(`/${username}/students`, { full });
+    }
+
+    async getQuestions(username: string, full = false): Promise<QuestionsResponse> {
+        return this.get<QuestionsResponse>(`/${username}/questions`, { full });
+    }
+
+    async getStudentJoinRequests(username: string, classId: string): Promise<JoinRequestsResponse> {
+        return this.get<JoinRequestsResponse>(`/${username}/joinRequests/${classId}`);
+    }
+
+    async updateStudentJoinRequest(
+        teacherUsername: string,
+        classId: string,
+        studentUsername: string,
+        accepted: boolean,
+    ): Promise<JoinRequestResponse> {
+        return this.put<JoinRequestResponse>(
+            `/${teacherUsername}/joinRequests/${classId}/${studentUsername}`,
+            accepted,
+        );
+    }
+
+    // GetInvitations(id: string) {return this.get<{ invitations: string[] }>(`/${id}/invitations`);}
+}
diff --git a/frontend/src/controllers/themes.ts b/frontend/src/controllers/themes.ts
index d6c8be98..bb76249d 100644
--- a/frontend/src/controllers/themes.ts
+++ b/frontend/src/controllers/themes.ts
@@ -1,11 +1,12 @@
 import { BaseController } from "@/controllers/base-controller.ts";
+import type { Theme } from "@dwengo-1/interfaces/theme";
 
 export class ThemeController extends BaseController {
     constructor() {
         super("theme");
     }
 
-    async getAll(language: string | null = null): Promise<unknown> {
+    async getAll(language: string | null = null): Promise<Theme[]> {
         const query = language ? { language } : undefined;
         return this.get("/", query);
     }
diff --git a/frontend/src/queries/students.ts b/frontend/src/queries/students.ts
new file mode 100644
index 00000000..822083d9
--- /dev/null
+++ b/frontend/src/queries/students.ts
@@ -0,0 +1,205 @@
+import { computed, toValue } from "vue";
+import type { MaybeRefOrGetter } from "vue";
+import {
+    useMutation,
+    type UseMutationReturnType,
+    useQuery,
+    useQueryClient,
+    type UseQueryReturnType,
+} from "@tanstack/vue-query";
+import {
+    type JoinRequestResponse,
+    type JoinRequestsResponse,
+    StudentController,
+    type StudentResponse,
+    type StudentsResponse,
+} from "@/controllers/students.ts";
+import type { ClassesResponse } from "@/controllers/classes.ts";
+import type { AssignmentsResponse } from "@/controllers/assignments.ts";
+import type { GroupsResponse } from "@/controllers/groups.ts";
+import type { SubmissionsResponse } from "@/controllers/submissions.ts";
+import type { QuestionsResponse } from "@/controllers/questions.ts";
+import type { StudentDTO } from "@dwengo-1/interfaces/student";
+
+const studentController = new StudentController();
+
+/** 🔑 Query keys */
+function studentsQueryKey(full: boolean): [string, boolean] {
+    return ["students", full];
+}
+function studentQueryKey(username: string): [string, string] {
+    return ["student", username];
+}
+function studentClassesQueryKey(username: string, full: boolean): [string, string, boolean] {
+    return ["student-classes", username, full];
+}
+function studentAssignmentsQueryKey(username: string, full: boolean): [string, string, boolean] {
+    return ["student-assignments", username, full];
+}
+function studentGroupsQueryKeys(username: string, full: boolean): [string, string, boolean] {
+    return ["student-groups", username, full];
+}
+function studentSubmissionsQueryKey(username: string): [string, string] {
+    return ["student-submissions", username];
+}
+function studentQuestionsQueryKey(username: string, full: boolean): [string, string, boolean] {
+    return ["student-questions", username, full];
+}
+export function studentJoinRequestsQueryKey(username: string): [string, string] {
+    return ["student-join-requests", username];
+}
+export function studentJoinRequestQueryKey(username: string, classId: string): [string, string, string] {
+    return ["student-join-request", username, classId];
+}
+
+export function useStudentsQuery(full: MaybeRefOrGetter<boolean> = true): UseQueryReturnType<StudentsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentsQueryKey(toValue(full))),
+        queryFn: async () => studentController.getAll(toValue(full)),
+    });
+}
+
+export function useStudentQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+): UseQueryReturnType<StudentResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentQueryKey(toValue(username)!)),
+        queryFn: async () => studentController.getByUsername(toValue(username)!),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useStudentClassesQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    full: MaybeRefOrGetter<boolean> = true,
+): UseQueryReturnType<ClassesResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentClassesQueryKey(toValue(username)!, toValue(full))),
+        queryFn: async () => studentController.getClasses(toValue(username)!, toValue(full)),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useStudentAssignmentsQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    full: MaybeRefOrGetter<boolean> = true,
+): UseQueryReturnType<AssignmentsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentAssignmentsQueryKey(toValue(username)!, toValue(full))),
+        queryFn: async () => studentController.getAssignments(toValue(username)!, toValue(full)),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useStudentGroupsQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    full: MaybeRefOrGetter<boolean> = true,
+): UseQueryReturnType<GroupsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentGroupsQueryKeys(toValue(username)!, toValue(full))),
+        queryFn: async () => studentController.getGroups(toValue(username)!, toValue(full)),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useStudentSubmissionsQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+): UseQueryReturnType<SubmissionsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentSubmissionsQueryKey(toValue(username)!)),
+        queryFn: async () => studentController.getSubmissions(toValue(username)!),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useStudentQuestionsQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    full: MaybeRefOrGetter<boolean> = true,
+): UseQueryReturnType<QuestionsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentQuestionsQueryKey(toValue(username)!, toValue(full))),
+        queryFn: async () => studentController.getQuestions(toValue(username)!, toValue(full)),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useStudentJoinRequestsQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+): UseQueryReturnType<JoinRequestsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentJoinRequestsQueryKey(toValue(username)!)),
+        queryFn: async () => studentController.getJoinRequests(toValue(username)!),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useStudentJoinRequestQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    classId: MaybeRefOrGetter<string | undefined>,
+): UseQueryReturnType<JoinRequestResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => studentJoinRequestQueryKey(toValue(username)!, toValue(classId)!)),
+        queryFn: async () => studentController.getJoinRequest(toValue(username)!, toValue(classId)!),
+        enabled: () => Boolean(toValue(username)) && Boolean(toValue(classId)),
+    });
+}
+
+export function useCreateStudentMutation(): UseMutationReturnType<StudentResponse, Error, StudentDTO, unknown> {
+    const queryClient = useQueryClient();
+
+    return useMutation({
+        mutationFn: async (data) => studentController.createStudent(data),
+        onSuccess: async () => {
+            await queryClient.invalidateQueries({ queryKey: ["students"] });
+        },
+    });
+}
+
+export function useDeleteStudentMutation(): UseMutationReturnType<StudentResponse, Error, string, unknown> {
+    const queryClient = useQueryClient();
+
+    return useMutation({
+        mutationFn: async (username) => studentController.deleteStudent(username),
+        onSuccess: async (deletedUser) => {
+            await queryClient.invalidateQueries({ queryKey: ["students"] });
+            await queryClient.invalidateQueries({ queryKey: studentQueryKey(deletedUser.student.username) });
+        },
+    });
+}
+
+export function useCreateJoinRequestMutation(): UseMutationReturnType<
+    JoinRequestResponse,
+    Error,
+    { username: string; classId: string },
+    unknown
+> {
+    const queryClient = useQueryClient();
+
+    return useMutation({
+        mutationFn: async ({ username, classId }) => studentController.createJoinRequest(username, classId),
+        onSuccess: async (newJoinRequest) => {
+            await queryClient.invalidateQueries({
+                queryKey: studentJoinRequestsQueryKey(newJoinRequest.request.requester),
+            });
+        },
+    });
+}
+
+export function useDeleteJoinRequestMutation(): UseMutationReturnType<
+    JoinRequestResponse,
+    Error,
+    { username: string; classId: string },
+    unknown
+> {
+    const queryClient = useQueryClient();
+
+    return useMutation({
+        mutationFn: async ({ username, classId }) => studentController.deleteJoinRequest(username, classId),
+        onSuccess: async (deletedJoinRequest) => {
+            const username = deletedJoinRequest.request.requester;
+            const classId = deletedJoinRequest.request.class;
+            await queryClient.invalidateQueries({ queryKey: studentJoinRequestsQueryKey(username) });
+            await queryClient.invalidateQueries({ queryKey: studentJoinRequestQueryKey(username, classId) });
+        },
+    });
+}
diff --git a/frontend/src/queries/teachers.ts b/frontend/src/queries/teachers.ts
new file mode 100644
index 00000000..778b2cba
--- /dev/null
+++ b/frontend/src/queries/teachers.ts
@@ -0,0 +1,136 @@
+import { computed, toValue } from "vue";
+import type { MaybeRefOrGetter } from "vue";
+import { useMutation, useQuery, useQueryClient, UseMutationReturnType, UseQueryReturnType } from "@tanstack/vue-query";
+import { TeacherController, type TeacherResponse, type TeachersResponse } from "@/controllers/teachers.ts";
+import type { ClassesResponse } from "@/controllers/classes.ts";
+import type { JoinRequestResponse, JoinRequestsResponse, StudentsResponse } from "@/controllers/students.ts";
+import type { QuestionsResponse } from "@/controllers/questions.ts";
+import type { TeacherDTO } from "@dwengo-1/interfaces/teacher";
+import { studentJoinRequestQueryKey, studentJoinRequestsQueryKey } from "@/queries/students.ts";
+
+const teacherController = new TeacherController();
+
+/** 🔑 Query keys */
+function teachersQueryKey(full: boolean): [string, boolean] {
+    return ["teachers", full];
+}
+
+function teacherQueryKey(username: string): [string, string] {
+    return ["teacher", username];
+}
+
+function teacherClassesQueryKey(username: string, full: boolean): [string, string, boolean] {
+    return ["teacher-classes", username, full];
+}
+
+function teacherStudentsQueryKey(username: string, full: boolean): [string, string, boolean] {
+    return ["teacher-students", username, full];
+}
+
+function teacherQuestionsQueryKey(username: string, full: boolean): [string, string, boolean] {
+    return ["teacher-questions", username, full];
+}
+
+export function useTeachersQuery(full: MaybeRefOrGetter<boolean> = false): UseQueryReturnType<TeachersResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => teachersQueryKey(toValue(full))),
+        queryFn: async () => teacherController.getAll(toValue(full)),
+    });
+}
+
+export function useTeacherQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+): UseQueryReturnType<TeacherResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => teacherQueryKey(toValue(username)!)),
+        queryFn: async () => teacherController.getByUsername(toValue(username)!),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useTeacherClassesQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    full: MaybeRefOrGetter<boolean> = false,
+): UseQueryReturnType<ClassesResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => teacherClassesQueryKey(toValue(username)!, toValue(full))),
+        queryFn: async () => teacherController.getClasses(toValue(username)!, toValue(full)),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useTeacherStudentsQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    full: MaybeRefOrGetter<boolean> = false,
+): UseQueryReturnType<StudentsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => teacherStudentsQueryKey(toValue(username)!, toValue(full))),
+        queryFn: async () => teacherController.getStudents(toValue(username)!, toValue(full)),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useTeacherQuestionsQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    full: MaybeRefOrGetter<boolean> = false,
+): UseQueryReturnType<QuestionsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => teacherQuestionsQueryKey(toValue(username)!, toValue(full))),
+        queryFn: async () => teacherController.getQuestions(toValue(username)!, toValue(full)),
+        enabled: () => Boolean(toValue(username)),
+    });
+}
+
+export function useTeacherJoinRequestsQuery(
+    username: MaybeRefOrGetter<string | undefined>,
+    classId: MaybeRefOrGetter<string | undefined>,
+): UseQueryReturnType<JoinRequestsResponse, Error> {
+    return useQuery({
+        queryKey: computed(() => JOIN_REQUESTS_QUERY_KEY(toValue(username)!, toValue(classId)!)),
+        queryFn: async () => teacherController.getStudentJoinRequests(toValue(username)!, toValue(classId)!),
+        enabled: () => Boolean(toValue(username)) && Boolean(toValue(classId)),
+    });
+}
+
+export function useCreateTeacherMutation(): UseMutationReturnType<TeacherResponse, Error, TeacherDTO, unknown> {
+    const queryClient = useQueryClient();
+
+    return useMutation({
+        mutationFn: async (data: TeacherDTO) => teacherController.createTeacher(data),
+        onSuccess: async () => {
+            await queryClient.invalidateQueries({ queryKey: ["teachers"] });
+        },
+    });
+}
+
+export function useDeleteTeacherMutation(): UseMutationReturnType<TeacherResponse, Error, string, unknown> {
+    const queryClient = useQueryClient();
+
+    return useMutation({
+        mutationFn: async (username: string) => teacherController.deleteTeacher(username),
+        onSuccess: async (deletedTeacher) => {
+            await queryClient.invalidateQueries({ queryKey: ["teachers"] });
+            await queryClient.invalidateQueries({ queryKey: teacherQueryKey(deletedTeacher.teacher.username) });
+        },
+    });
+}
+
+export function useUpdateJoinRequestMutation(): UseMutationReturnType<
+    JoinRequestResponse,
+    Error,
+    { teacherUsername: string; classId: string; studentUsername: string; accepted: boolean },
+    unknown
+> {
+    const queryClient = useQueryClient();
+
+    return useMutation({
+        mutationFn: async ({ teacherUsername, classId, studentUsername, accepted }) =>
+            teacherController.updateStudentJoinRequest(teacherUsername, classId, studentUsername, accepted),
+        onSuccess: async (deletedJoinRequest) => {
+            const username = deletedJoinRequest.request.requester;
+            const classId = deletedJoinRequest.request.class;
+            await queryClient.invalidateQueries({ queryKey: studentJoinRequestsQueryKey(username) });
+            await queryClient.invalidateQueries({ queryKey: studentJoinRequestQueryKey(username, classId) });
+        },
+    });
+}
diff --git a/frontend/src/queries/themes.ts b/frontend/src/queries/themes.ts
index a9c50f23..c3be25ae 100644
--- a/frontend/src/queries/themes.ts
+++ b/frontend/src/queries/themes.ts
@@ -1,11 +1,11 @@
 import { useQuery, type UseQueryReturnType } from "@tanstack/vue-query";
-import { getThemeController } from "@/controllers/controllers";
 import { type MaybeRefOrGetter, toValue } from "vue";
-import type { Theme } from "@/data-objects/theme.ts";
+import type { Theme } from "@dwengo-1/interfaces/theme";
+import { getThemeController } from "@/controllers/controllers.ts";
 
 const themeController = getThemeController();
 
-export function useThemeQuery(language: MaybeRefOrGetter<string>): UseQueryReturnType<Theme[], Error> {
+export function useThemeQuery(language: MaybeRefOrGetter<string | undefined>): UseQueryReturnType<Theme[], Error> {
     return useQuery({
         queryKey: ["themes", language],
         queryFn: async () => {
@@ -16,10 +16,12 @@ export function useThemeQuery(language: MaybeRefOrGetter<string>): UseQueryRetur
     });
 }
 
-export function useThemeHruidsQuery(themeKey: string | null): UseQueryReturnType<unknown, Error> {
+export function useThemeHruidsQuery(
+    themeKey: MaybeRefOrGetter<string | undefined>,
+): UseQueryReturnType<string[], Error> {
     return useQuery({
         queryKey: ["theme-hruids", themeKey],
-        queryFn: async () => themeController.getHruidsByKey(themeKey!),
+        queryFn: async () => themeController.getHruidsByKey(toValue(themeKey)!),
         enabled: Boolean(themeKey),
     });
 }