diff --git a/backend/src/controllers/assignments.ts b/backend/src/controllers/assignments.ts
index 1520fc10..2ecb35cb 100644
--- a/backend/src/controllers/assignments.ts
+++ b/backend/src/controllers/assignments.ts
@@ -1,77 +1,94 @@
 import { Request, Response } from 'express';
-import { createAssignment, getAllAssignments, getAssignment, getAssignmentsSubmissions } from '../services/assignments.js';
+import {
+    createAssignment,
+    deleteAssignment,
+    getAllAssignments,
+    getAssignment,
+    getAssignmentsSubmissions,
+    putAssignment,
+} from '../services/assignments.js';
 import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
+import { requireFields } from './error-helper.js';
+import { BadRequestException } from '../exceptions/bad-request-exception.js';
+import { Assignment } from '../entities/assignments/assignment.entity.js';
+import { EntityDTO } from '@mikro-orm/core';
 
-// Typescript is annoying with parameter forwarding from class.ts
-interface AssignmentParams {
-    classid: string;
-    id: string;
-}
-
-export async function getAllAssignmentsHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
-    const classid = req.params.classid;
+export async function getAllAssignmentsHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.classid;
     const full = req.query.full === 'true';
 
-    const assignments = await getAllAssignments(classid, full);
+    const assignments = await getAllAssignments(classId, full);
 
-    res.json({
-        assignments: assignments,
-    });
+    res.json({ assignments });
 }
 
-export async function createAssignmentHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
+export async function createAssignmentHandler(req: Request, res: Response): Promise<void> {
     const classid = req.params.classid;
+    const description = req.body.description;
+    const language = req.body.language;
+    const learningPath = req.body.learningPath;
+    const title = req.body.title;
+
+    requireFields({ description, language, learningPath, title });
+
     const assignmentData = req.body as AssignmentDTO;
-
-    if (!assignmentData.description || !assignmentData.language || !assignmentData.learningPath || !assignmentData.title) {
-        res.status(400).json({
-            error: 'Missing one or more required fields: title, description, learningPath, language',
-        });
-        return;
-    }
-
     const assignment = await createAssignment(classid, assignmentData);
 
-    if (!assignment) {
-        res.status(500).json({ error: 'Could not create assignment ' });
-        return;
-    }
-
-    res.status(201).json(assignment);
+    res.json({ assignment });
 }
 
-export async function getAssignmentHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
+export async function getAssignmentHandler(req: Request, res: Response): Promise<void> {
     const id = Number(req.params.id);
     const classid = req.params.classid;
+    requireFields({ id, classid });
 
     if (isNaN(id)) {
-        res.status(400).json({ error: 'Assignment id must be a number' });
-        return;
+        throw new BadRequestException('Assignment id should be a number');
     }
 
     const assignment = await getAssignment(classid, id);
 
-    if (!assignment) {
-        res.status(404).json({ error: 'Assignment not found' });
-        return;
-    }
-
-    res.json(assignment);
+    res.json({ assignment });
 }
 
-export async function getAssignmentsSubmissionsHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
+export async function putAssignmentHandler(req: Request, res: Response): Promise<void> {
+    const id = Number(req.params.id);
+    const classid = req.params.classid;
+    requireFields({ id, classid });
+
+    if (isNaN(id)) {
+        throw new BadRequestException('Assignment id should be a number');
+    }
+
+    const assignmentData = req.body as Partial<EntityDTO<Assignment>>;
+    const assignment = await putAssignment(classid, id, assignmentData);
+
+    res.json({ assignment });
+}
+
+export async function deleteAssignmentHandler(req: Request, _res: Response): Promise<void> {
+    const id = Number(req.params.id);
+    const classid = req.params.classid;
+    requireFields({ id, classid });
+
+    if (isNaN(id)) {
+        throw new BadRequestException('Assignment id should be a number');
+    }
+
+    await deleteAssignment(classid, id);
+}
+
+export async function getAssignmentsSubmissionsHandler(req: Request, res: Response): Promise<void> {
     const classid = req.params.classid;
     const assignmentNumber = Number(req.params.id);
     const full = req.query.full === 'true';
+    requireFields({ assignmentNumber, classid });
 
     if (isNaN(assignmentNumber)) {
-        res.status(400).json({ error: 'Assignment id must be a number' });
-        return;
+        throw new BadRequestException('Assignment id should be a number');
     }
 
     const submissions = await getAssignmentsSubmissions(classid, assignmentNumber, full);
 
-    res.json({
-        submissions: submissions,
-    });
+    res.json({ submissions });
 }
diff --git a/backend/src/controllers/classes.ts b/backend/src/controllers/classes.ts
index 03e88a52..6f253547 100644
--- a/backend/src/controllers/classes.ts
+++ b/backend/src/controllers/classes.ts
@@ -1,44 +1,62 @@
 import { Request, Response } from 'express';
-import { createClass, getAllClasses, getClass, getClassStudents, getClassStudentsIds, getClassTeacherInvitations } from '../services/classes.js';
+import {
+    addClassStudent,
+    addClassTeacher,
+    createClass,
+    deleteClass,
+    deleteClassStudent,
+    deleteClassTeacher,
+    getAllClasses,
+    getClass,
+    getClassStudents,
+    getClassTeacherInvitations,
+    getClassTeachers,
+    putClass,
+} from '../services/classes.js';
 import { ClassDTO } from '@dwengo-1/common/interfaces/class';
+import { requireFields } from './error-helper.js';
+import { EntityDTO } from '@mikro-orm/core';
+import { Class } from '../entities/classes/class.entity.js';
 
 export async function getAllClassesHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
     const classes = await getAllClasses(full);
 
-    res.json({
-        classes: classes,
-    });
+    res.json({ classes });
 }
 
 export async function createClassHandler(req: Request, res: Response): Promise<void> {
+    const displayName = req.body.displayName;
+    requireFields({ displayName });
+
     const classData = req.body as ClassDTO;
-
-    if (!classData.displayName) {
-        res.status(400).json({
-            error: 'Missing one or more required fields: displayName',
-        });
-        return;
-    }
-
     const cls = await createClass(classData);
 
-    if (!cls) {
-        res.status(500).json({ error: 'Something went wrong while creating class' });
-        return;
-    }
-
-    res.status(201).json({ class: cls });
+    res.json({ class: cls });
 }
 
 export async function getClassHandler(req: Request, res: Response): Promise<void> {
     const classId = req.params.id;
+    requireFields({ classId });
+
     const cls = await getClass(classId);
 
-    if (!cls) {
-        res.status(404).json({ error: 'Class not found' });
-        return;
-    }
+    res.json({ class: cls });
+}
+
+export async function putClassHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.id;
+    requireFields({ classId });
+
+    const newData = req.body as Partial<EntityDTO<Class>>;
+    const cls = await putClass(classId, newData);
+
+    res.json({ class: cls });
+}
+
+export async function deleteClassHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.id;
+    const cls = await deleteClass(classId);
 
     res.json({ class: cls });
 }
@@ -46,21 +64,69 @@ export async function getClassHandler(req: Request, res: Response): Promise<void
 export async function getClassStudentsHandler(req: Request, res: Response): Promise<void> {
     const classId = req.params.id;
     const full = req.query.full === 'true';
+    requireFields({ classId });
 
-    const students = full ? await getClassStudents(classId) : await getClassStudentsIds(classId);
+    const students = await getClassStudents(classId, full);
 
-    res.json({
-        students: students,
-    });
+    res.json({ students });
+}
+
+export async function getClassTeachersHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.id;
+    const full = req.query.full === 'true';
+    requireFields({ classId });
+
+    const teachers = await getClassTeachers(classId, full);
+
+    res.json({ teachers });
 }
 
 export async function getTeacherInvitationsHandler(req: Request, res: Response): Promise<void> {
     const classId = req.params.id;
     const full = req.query.full === 'true';
+    requireFields({ classId });
 
     const invitations = await getClassTeacherInvitations(classId, full);
 
-    res.json({
-        invitations: invitations,
-    });
+    res.json({ invitations });
+}
+
+export async function deleteClassStudentHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.id;
+    const username = req.params.username;
+    requireFields({ classId, username });
+
+    const cls = await deleteClassStudent(classId, username);
+
+    res.json({ class: cls });
+}
+
+export async function deleteClassTeacherHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.id;
+    const username = req.params.username;
+    requireFields({ classId, username });
+
+    const cls = await deleteClassTeacher(classId, username);
+
+    res.json({ class: cls });
+}
+
+export async function addClassStudentHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.id;
+    const username = req.body.username;
+    requireFields({ classId, username });
+
+    const cls = await addClassStudent(classId, username);
+
+    res.json({ class: cls });
+}
+
+export async function addClassTeacherHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.id;
+    const username = req.body.username;
+    requireFields({ classId, username });
+
+    const cls = await addClassTeacher(classId, username);
+
+    res.json({ class: cls });
 }
diff --git a/backend/src/controllers/groups.ts b/backend/src/controllers/groups.ts
index 989066a6..ec177dcc 100644
--- a/backend/src/controllers/groups.ts
+++ b/backend/src/controllers/groups.ts
@@ -1,100 +1,104 @@
 import { Request, Response } from 'express';
-import { createGroup, getAllGroups, getGroup, getGroupSubmissions } from '../services/groups.js';
+import { createGroup, deleteGroup, getAllGroups, getGroup, getGroupSubmissions, putGroup } from '../services/groups.js';
 import { GroupDTO } from '@dwengo-1/common/interfaces/group';
+import { requireFields } from './error-helper.js';
+import { BadRequestException } from '../exceptions/bad-request-exception.js';
+import { EntityDTO } from '@mikro-orm/core';
+import { Group } from '../entities/assignments/group.entity.js';
 
-// Typescript is annoywith with parameter forwarding from class.ts
-interface GroupParams {
-    classid: string;
-    assignmentid: string;
-    groupid?: string;
-}
-
-export async function getGroupHandler(req: Request<GroupParams>, res: Response): Promise<void> {
-    const classId = req.params.classid;
-    const full = req.query.full === 'true';
-    const assignmentId = Number(req.params.assignmentid);
+function checkGroupFields(classId: string, assignmentId: number, groupId: number): void {
+    requireFields({ classId, assignmentId, groupId });
 
     if (isNaN(assignmentId)) {
-        res.status(400).json({ error: 'Assignment id must be a number' });
-        return;
+        throw new BadRequestException('Assignment id must be a number');
     }
 
-    const groupId = Number(req.params.groupid!); // Can't be undefined
-
     if (isNaN(groupId)) {
-        res.status(400).json({ error: 'Group id must be a number' });
-        return;
+        throw new BadRequestException('Group id must be a number');
     }
+}
 
-    const group = await getGroup(classId, assignmentId, groupId, full);
+export async function getGroupHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.classid;
+    const assignmentId = parseInt(req.params.assignmentid);
+    const groupId = parseInt(req.params.groupid);
+    checkGroupFields(classId, assignmentId, groupId);
 
-    if (!group) {
-        res.status(404).json({ error: 'Group not found' });
-        return;
-    }
+    const group = await getGroup(classId, assignmentId, groupId);
 
-    res.json(group);
+    res.json({ group });
+}
+
+export async function putGroupHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.classid;
+    const assignmentId = parseInt(req.params.assignmentid);
+    const groupId = parseInt(req.params.groupid);
+    checkGroupFields(classId, assignmentId, groupId);
+
+    const group = await putGroup(classId, assignmentId, groupId, req.body as Partial<EntityDTO<Group>>);
+
+    res.json({ group });
+}
+
+export async function deleteGroupHandler(req: Request, res: Response): Promise<void> {
+    const classId = req.params.classid;
+    const assignmentId = parseInt(req.params.assignmentid);
+    const groupId = parseInt(req.params.groupid);
+    checkGroupFields(classId, assignmentId, groupId);
+
+    const group = await deleteGroup(classId, assignmentId, groupId);
+
+    res.json({ group });
 }
 
 export async function getAllGroupsHandler(req: Request, res: Response): Promise<void> {
     const classId = req.params.classid;
-    const full = req.query.full === 'true';
-
     const assignmentId = Number(req.params.assignmentid);
+    const full = req.query.full === 'true';
+    requireFields({ classId, assignmentId });
 
     if (isNaN(assignmentId)) {
-        res.status(400).json({ error: 'Assignment id must be a number' });
-        return;
+        throw new BadRequestException('Assignment id must be a number');
     }
 
     const groups = await getAllGroups(classId, assignmentId, full);
 
-    res.json({
-        groups: groups,
-    });
+    res.json({ groups });
 }
 
 export async function createGroupHandler(req: Request, res: Response): Promise<void> {
     const classid = req.params.classid;
     const assignmentId = Number(req.params.assignmentid);
 
+    requireFields({ classid, assignmentId });
+
     if (isNaN(assignmentId)) {
-        res.status(400).json({ error: 'Assignment id must be a number' });
-        return;
+        throw new BadRequestException('Assignment id must be a number');
     }
 
     const groupData = req.body as GroupDTO;
     const group = await createGroup(groupData, classid, assignmentId);
 
-    if (!group) {
-        res.status(500).json({ error: 'Something went wrong while creating group' });
-        return;
-    }
-
-    res.status(201).json(group);
+    res.status(201).json({ group });
 }
 
 export async function getGroupSubmissionsHandler(req: Request, res: Response): Promise<void> {
     const classId = req.params.classid;
+    const assignmentId = Number(req.params.assignmentid);
+    const groupId = Number(req.params.groupid);
     const full = req.query.full === 'true';
 
-    const assignmentId = Number(req.params.assignmentid);
+    requireFields({ classId, assignmentId, groupId });
 
     if (isNaN(assignmentId)) {
-        res.status(400).json({ error: 'Assignment id must be a number' });
-        return;
+        throw new BadRequestException('Assignment id must be a number');
     }
 
-    const groupId = Number(req.params.groupid); // Can't be undefined
-
     if (isNaN(groupId)) {
-        res.status(400).json({ error: 'Group id must be a number' });
-        return;
+        throw new BadRequestException('Group id must be a number');
     }
 
     const submissions = await getGroupSubmissions(classId, assignmentId, groupId, full);
 
-    res.json({
-        submissions: submissions,
-    });
+    res.json({ submissions });
 }
diff --git a/backend/src/controllers/submissions.ts b/backend/src/controllers/submissions.ts
index 239eb6d7..fb681656 100644
--- a/backend/src/controllers/submissions.ts
+++ b/backend/src/controllers/submissions.ts
@@ -1,61 +1,61 @@
 import { Request, Response } from 'express';
-import { createSubmission, deleteSubmission, getSubmission } from '../services/submissions.js';
-import { SubmissionDTO } from '@dwengo-1/common/interfaces/submission';
+import { createSubmission, deleteSubmission, getAllSubmissions, getSubmission } from '../services/submissions.js';
+import { BadRequestException } from '../exceptions/bad-request-exception.js';
+import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
 import { Language, languageMap } from '@dwengo-1/common/util/language';
+import { SubmissionDTO } from '@dwengo-1/common/interfaces/submission';
+import { requireFields } from './error-helper.js';
 
-interface SubmissionParams {
-    hruid: string;
-    id: number;
-}
-
-export async function getSubmissionHandler(req: Request<SubmissionParams>, res: Response): Promise<void> {
+export async function getSubmissionHandler(req: Request, res: Response): Promise<void> {
     const lohruid = req.params.hruid;
-    const submissionNumber = Number(req.params.id);
-
-    if (isNaN(submissionNumber)) {
-        res.status(400).json({ error: 'Submission number is not a number' });
-        return;
-    }
-
     const lang = languageMap[req.query.language as string] || Language.Dutch;
     const version = (req.query.version || 1) as number;
+    const submissionNumber = Number(req.params.id);
+    requireFields({ lohruid, submissionNumber });
 
-    const submission = await getSubmission(lohruid, lang, version, submissionNumber);
-
-    if (!submission) {
-        res.status(404).json({ error: 'Submission not found' });
-        return;
+    if (isNaN(submissionNumber)) {
+        throw new BadRequestException('Submission number must be a number');
     }
 
-    res.json(submission);
+    const loId = new LearningObjectIdentifier(lohruid, lang, version);
+    const submission = await getSubmission(loId, submissionNumber);
+
+    res.json({ submission });
 }
 
+export async function getAllSubmissionsHandler(req: Request, res: Response): Promise<void> {
+    const lohruid = req.params.hruid;
+    const lang = languageMap[req.query.language as string] || Language.Dutch;
+    const version = (req.query.version || 1) as number;
+    requireFields({ lohruid });
+
+    const loId = new LearningObjectIdentifier(lohruid, lang, version);
+    const submissions = await getAllSubmissions(loId);
+
+    res.json({ submissions });
+}
+
+// TODO: gerald moet nog dingen toevoegen aan de databank voor dat dit gefinaliseerd kan worden
 export async function createSubmissionHandler(req: Request, res: Response): Promise<void> {
     const submissionDTO = req.body as SubmissionDTO;
-
     const submission = await createSubmission(submissionDTO);
 
-    if (!submission) {
-        res.status(400).json({ error: 'Failed to create submission' });
-        return;
-    }
-
-    res.json(submission);
+    res.json({ submission });
 }
 
 export async function deleteSubmissionHandler(req: Request, res: Response): Promise<void> {
     const hruid = req.params.hruid;
-    const submissionNumber = Number(req.params.id);
-
     const lang = languageMap[req.query.language as string] || Language.Dutch;
     const version = (req.query.version || 1) as number;
+    const submissionNumber = Number(req.params.id);
+    requireFields({ hruid, submissionNumber });
 
-    const submission = await deleteSubmission(hruid, lang, version, submissionNumber);
-
-    if (!submission) {
-        res.status(404).json({ error: 'Submission not found' });
-        return;
+    if (isNaN(submissionNumber)) {
+        throw new BadRequestException('Submission number must be a number');
     }
 
-    res.json(submission);
+    const loId = new LearningObjectIdentifier(hruid, lang, version);
+    const submission = await deleteSubmission(loId, submissionNumber);
+
+    res.json({ submission });
 }
diff --git a/backend/src/controllers/teachers.ts b/backend/src/controllers/teachers.ts
index 9275ca92..c8063f80 100644
--- a/backend/src/controllers/teachers.ts
+++ b/backend/src/controllers/teachers.ts
@@ -81,16 +81,15 @@ export async function getTeacherQuestionHandler(req: Request, res: Response): Pr
 }
 
 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 });
+    requireFields({ 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 studentUsername = req.params.studentUsername;
     const classId = req.params.classId;
     const accepted = req.body.accepted !== 'false'; // Default = true
     requireFields({ studentUsername, classId });
diff --git a/backend/src/data/assignments/submission-repository.ts b/backend/src/data/assignments/submission-repository.ts
index f5090adc..2e673210 100644
--- a/backend/src/data/assignments/submission-repository.ts
+++ b/backend/src/data/assignments/submission-repository.ts
@@ -17,6 +17,14 @@ export class SubmissionRepository extends DwengoEntityRepository<Submission> {
         });
     }
 
+    public async findByLearningObject(loId: LearningObjectIdentifier): Promise<Submission[]> {
+        return this.find({
+            learningObjectHruid: loId.hruid,
+            learningObjectLanguage: loId.language,
+            learningObjectVersion: loId.version,
+        });
+    }
+
     public async findMostRecentSubmissionForStudent(loId: LearningObjectIdentifier, submitter: Student): Promise<Submission | null> {
         return this.findOne(
             {
diff --git a/backend/src/data/questions/question-repository.ts b/backend/src/data/questions/question-repository.ts
index cf9ecab0..01e38df2 100644
--- a/backend/src/data/questions/question-repository.ts
+++ b/backend/src/data/questions/question-repository.ts
@@ -3,6 +3,7 @@ import { Question } from '../../entities/questions/question.entity.js';
 import { LearningObjectIdentifier } from '../../entities/content/learning-object-identifier.js';
 import { Student } from '../../entities/users/student.entity.js';
 import { LearningObject } from '../../entities/content/learning-object.entity.js';
+import { Assignment } from '../../entities/assignments/assignment.entity.js';
 import { Loaded } from '@mikro-orm/core';
 
 export class QuestionRepository extends DwengoEntityRepository<Question> {
@@ -56,6 +57,14 @@ export class QuestionRepository extends DwengoEntityRepository<Question> {
         });
     }
 
+    public async findAllByAssignment(assignment: Assignment): Promise<Question[]> {
+        return this.find({
+            author: assignment.groups.flatMap((group) => group.members),
+            learningObjectHruid: assignment.learningPathHruid,
+            learningObjectLanguage: assignment.learningPathLanguage,
+        });
+    }
+
     public async findAllByAuthor(author: Student): Promise<Question[]> {
         return this.findAll({
             where: { author },
diff --git a/backend/src/interfaces/assignment.ts b/backend/src/interfaces/assignment.ts
index d48a9083..7abb3d3c 100644
--- a/backend/src/interfaces/assignment.ts
+++ b/backend/src/interfaces/assignment.ts
@@ -8,19 +8,18 @@ import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
 export function mapToAssignmentDTOId(assignment: Assignment): AssignmentDTO {
     return {
         id: assignment.id!,
-        class: assignment.within.classId!,
+        within: assignment.within.classId!,
         title: assignment.title,
         description: assignment.description,
         learningPath: assignment.learningPathHruid,
         language: assignment.learningPathLanguage,
-        // Groups: assignment.groups.map(group => group.groupNumber),
     };
 }
 
 export function mapToAssignmentDTO(assignment: Assignment): AssignmentDTO {
     return {
         id: assignment.id!,
-        class: assignment.within.classId!,
+        within: assignment.within.classId!,
         title: assignment.title,
         description: assignment.description,
         learningPath: assignment.learningPathHruid,
diff --git a/backend/src/interfaces/class.ts b/backend/src/interfaces/class.ts
index 7b07fcf2..76fa5fd5 100644
--- a/backend/src/interfaces/class.ts
+++ b/backend/src/interfaces/class.ts
@@ -10,7 +10,6 @@ export function mapToClassDTO(cls: Class): ClassDTO {
         displayName: cls.displayName,
         teachers: cls.teachers.map((teacher) => teacher.username),
         students: cls.students.map((student) => student.username),
-        joinRequests: [], // TODO
     };
 }
 
diff --git a/backend/src/interfaces/group.ts b/backend/src/interfaces/group.ts
index 1a169b2b..ac0efa64 100644
--- a/backend/src/interfaces/group.ts
+++ b/backend/src/interfaces/group.ts
@@ -1,11 +1,13 @@
 import { Group } from '../entities/assignments/group.entity.js';
 import { mapToAssignmentDTO } from './assignment.js';
+import { mapToClassDTO } from './class.js';
 import { mapToStudentDTO } from './student.js';
 import { GroupDTO } from '@dwengo-1/common/interfaces/group';
 
 export function mapToGroupDTO(group: Group): GroupDTO {
     return {
-        assignment: mapToAssignmentDTO(group.assignment), // ERROR: , group.assignment.within),
+        class: mapToClassDTO(group.assignment.within),
+        assignment: mapToAssignmentDTO(group.assignment),
         groupNumber: group.groupNumber!,
         members: group.members.map(mapToStudentDTO),
     };
@@ -13,6 +15,7 @@ export function mapToGroupDTO(group: Group): GroupDTO {
 
 export function mapToGroupDTOId(group: Group): GroupDTO {
     return {
+        class: group.assignment.within.classId!,
         assignment: group.assignment.id!,
         groupNumber: group.groupNumber!,
         members: group.members.map((member) => member.username),
diff --git a/backend/src/interfaces/submission.ts b/backend/src/interfaces/submission.ts
index b4ed4a2b..91882c35 100644
--- a/backend/src/interfaces/submission.ts
+++ b/backend/src/interfaces/submission.ts
@@ -1,6 +1,9 @@
+import { getSubmissionRepository } from '../data/repositories.js';
+import { Group } from '../entities/assignments/group.entity.js';
 import { Submission } from '../entities/assignments/submission.entity.js';
+import { Student } from '../entities/users/student.entity.js';
 import { mapToGroupDTO } from './group.js';
-import { mapToStudent, mapToStudentDTO } from './student.js';
+import { mapToStudentDTO } from './student.js';
 import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
 
 export function mapToSubmissionDTO(submission: Submission): SubmissionDTO {
@@ -29,17 +32,14 @@ export function mapToSubmissionDTOId(submission: Submission): SubmissionDTOId {
     };
 }
 
-export function mapToSubmission(submissionDTO: SubmissionDTO): Submission {
-    const submission = new Submission();
-    submission.learningObjectHruid = submissionDTO.learningObjectIdentifier.hruid;
-    submission.learningObjectLanguage = submissionDTO.learningObjectIdentifier.language;
-    submission.learningObjectVersion = submissionDTO.learningObjectIdentifier.version!;
-    // Submission.submissionNumber = submissionDTO.submissionNumber;
-    submission.submitter = mapToStudent(submissionDTO.submitter);
-    // Submission.submissionTime = submissionDTO.time;
-    // Submission.onBehalfOf =  submissionDTO.group!;
-    // TODO fix group
-    submission.content = submissionDTO.content;
-
-    return submission;
+export function mapToSubmission(submissionDTO: SubmissionDTO, submitter: Student, onBehalfOf: Group | undefined): Submission {
+    return getSubmissionRepository().create({
+        learningObjectHruid: submissionDTO.learningObjectIdentifier.hruid,
+        learningObjectLanguage: submissionDTO.learningObjectIdentifier.language,
+        learningObjectVersion: submissionDTO.learningObjectIdentifier.version || 1,
+        submitter: submitter,
+        submissionTime: new Date(),
+        content: submissionDTO.content,
+        onBehalfOf: onBehalfOf,
+    });
 }
diff --git a/backend/src/routes/assignments.ts b/backend/src/routes/assignments.ts
index 3652dcc6..083ee586 100644
--- a/backend/src/routes/assignments.ts
+++ b/backend/src/routes/assignments.ts
@@ -1,22 +1,26 @@
 import express from 'express';
 import {
     createAssignmentHandler,
+    deleteAssignmentHandler,
     getAllAssignmentsHandler,
     getAssignmentHandler,
     getAssignmentsSubmissionsHandler,
+    putAssignmentHandler,
 } from '../controllers/assignments.js';
 import groupRouter from './groups.js';
 
 const router = express.Router({ mergeParams: true });
 
-// Root endpoint used to search objects
 router.get('/', getAllAssignmentsHandler);
 
 router.post('/', createAssignmentHandler);
 
-// Information about an assignment with id 'id'
 router.get('/:id', getAssignmentHandler);
 
+router.put('/:id', putAssignmentHandler);
+
+router.delete('/:id', deleteAssignmentHandler);
+
 router.get('/:id/submissions', getAssignmentsSubmissionsHandler);
 
 router.get('/:id/questions', (_req, res) => {
diff --git a/backend/src/routes/classes.ts b/backend/src/routes/classes.ts
index e0972988..cef6fd72 100644
--- a/backend/src/routes/classes.ts
+++ b/backend/src/routes/classes.ts
@@ -1,10 +1,17 @@
 import express from 'express';
 import {
+    addClassStudentHandler,
+    addClassTeacherHandler,
     createClassHandler,
+    deleteClassHandler,
+    deleteClassStudentHandler,
+    deleteClassTeacherHandler,
     getAllClassesHandler,
     getClassHandler,
     getClassStudentsHandler,
+    getClassTeachersHandler,
     getTeacherInvitationsHandler,
+    putClassHandler,
 } from '../controllers/classes.js';
 import assignmentRouter from './assignments.js';
 
@@ -15,13 +22,26 @@ router.get('/', getAllClassesHandler);
 
 router.post('/', createClassHandler);
 
-// Information about an class with id 'id'
 router.get('/:id', getClassHandler);
 
+router.put('/:id', putClassHandler);
+
+router.delete('/:id', deleteClassHandler);
+
 router.get('/:id/teacher-invitations', getTeacherInvitationsHandler);
 
 router.get('/:id/students', getClassStudentsHandler);
 
+router.post('/:id/students', addClassStudentHandler);
+
+router.delete('/:id/students/:username', deleteClassStudentHandler);
+
+router.get('/:id/teachers', getClassTeachersHandler);
+
+router.post('/:id/teachers', addClassTeacherHandler);
+
+router.delete('/:id/teachers/:username', deleteClassTeacherHandler);
+
 router.use('/:classid/assignments', assignmentRouter);
 
 export default router;
diff --git a/backend/src/routes/groups.ts b/backend/src/routes/groups.ts
index 1486edce..7f973972 100644
--- a/backend/src/routes/groups.ts
+++ b/backend/src/routes/groups.ts
@@ -1,5 +1,12 @@
 import express from 'express';
-import { createGroupHandler, getAllGroupsHandler, getGroupHandler, getGroupSubmissionsHandler } from '../controllers/groups.js';
+import {
+    createGroupHandler,
+    deleteGroupHandler,
+    getAllGroupsHandler,
+    getGroupHandler,
+    getGroupSubmissionsHandler,
+    putGroupHandler,
+} from '../controllers/groups.js';
 
 const router = express.Router({ mergeParams: true });
 
@@ -8,16 +15,12 @@ router.get('/', getAllGroupsHandler);
 
 router.post('/', createGroupHandler);
 
-// Information about a group (members, ... [TODO DOC])
 router.get('/:groupid', getGroupHandler);
 
+router.put('/:groupid', putGroupHandler);
+
+router.delete('/:groupid', deleteGroupHandler);
+
 router.get('/:groupid/submissions', getGroupSubmissionsHandler);
 
-// The list of questions a group has made
-router.get('/:id/questions', (_req, res) => {
-    res.json({
-        questions: ['0'],
-    });
-});
-
 export default router;
diff --git a/backend/src/routes/submissions.ts b/backend/src/routes/submissions.ts
index 8e9831b9..7c91de52 100644
--- a/backend/src/routes/submissions.ts
+++ b/backend/src/routes/submissions.ts
@@ -1,13 +1,9 @@
 import express from 'express';
-import { createSubmissionHandler, deleteSubmissionHandler, getSubmissionHandler } from '../controllers/submissions.js';
+import { createSubmissionHandler, deleteSubmissionHandler, getAllSubmissionsHandler, getSubmissionHandler } from '../controllers/submissions.js';
 const router = express.Router({ mergeParams: true });
 
 // Root endpoint used to search objects
-router.get('/', (_req, res) => {
-    res.json({
-        submissions: ['0', '1'],
-    });
-});
+router.get('/', getAllSubmissionsHandler);
 
 router.post('/:id', createSubmissionHandler);
 
diff --git a/backend/src/services/assignments.ts b/backend/src/services/assignments.ts
index e86b69b2..5fd8f67f 100644
--- a/backend/src/services/assignments.ts
+++ b/backend/src/services/assignments.ts
@@ -1,18 +1,43 @@
-import { getAssignmentRepository, getClassRepository, getGroupRepository, getSubmissionRepository } from '../data/repositories.js';
-import { mapToAssignment, mapToAssignmentDTO, mapToAssignmentDTOId } from '../interfaces/assignment.js';
-import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
 import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
+import {
+    getAssignmentRepository,
+    getClassRepository,
+    getGroupRepository,
+    getQuestionRepository,
+    getSubmissionRepository,
+} from '../data/repositories.js';
+import { Assignment } from '../entities/assignments/assignment.entity.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
+import { mapToAssignment, mapToAssignmentDTO, mapToAssignmentDTOId } from '../interfaces/assignment.js';
+import { mapToQuestionDTO } from '../interfaces/question.js';
+import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
+import { fetchClass } from './classes.js';
+import { QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
 import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
-import { getLogger } from '../logging/initalize.js';
+import { EntityDTO } from '@mikro-orm/core';
+import { putObject } from './service-helper.js';
 
-export async function getAllAssignments(classid: string, full: boolean): Promise<AssignmentDTO[]> {
+export async function fetchAssignment(classid: string, assignmentNumber: number): Promise<Assignment> {
     const classRepository = getClassRepository();
     const cls = await classRepository.findById(classid);
 
     if (!cls) {
-        return [];
+        throw new NotFoundException("Could not find assignment's class");
     }
 
+    const assignmentRepository = getAssignmentRepository();
+    const assignment = await assignmentRepository.findByClassAndId(cls, assignmentNumber);
+
+    if (!assignment) {
+        throw new NotFoundException('Could not find assignment');
+    }
+
+    return assignment;
+}
+
+export async function getAllAssignments(classid: string, full: boolean): Promise<AssignmentDTO[]> {
+    const cls = await fetchClass(classid);
+
     const assignmentRepository = getAssignmentRepository();
     const assignments = await assignmentRepository.findAllAssignmentsInClass(cls);
 
@@ -23,42 +48,37 @@ export async function getAllAssignments(classid: string, full: boolean): Promise
     return assignments.map(mapToAssignmentDTOId);
 }
 
-export async function createAssignment(classid: string, assignmentData: AssignmentDTO): Promise<AssignmentDTO | null> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classid);
-
-    if (!cls) {
-        return null;
-    }
+export async function createAssignment(classid: string, assignmentData: AssignmentDTO): Promise<AssignmentDTO> {
+    const cls = await fetchClass(classid);
 
     const assignment = mapToAssignment(assignmentData, cls);
+
     const assignmentRepository = getAssignmentRepository();
+    const newAssignment = assignmentRepository.create(assignment);
+    await assignmentRepository.save(newAssignment, { preventOverwrite: true });
 
-    try {
-        const newAssignment = assignmentRepository.create(assignment);
-        await assignmentRepository.save(newAssignment);
-
-        return mapToAssignmentDTO(newAssignment);
-    } catch (e) {
-        getLogger().error(e);
-        return null;
-    }
+    return mapToAssignmentDTO(newAssignment);
 }
 
-export async function getAssignment(classid: string, id: number): Promise<AssignmentDTO | null> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classid);
+export async function getAssignment(classid: string, id: number): Promise<AssignmentDTO> {
+    const assignment = await fetchAssignment(classid, id);
+    return mapToAssignmentDTO(assignment);
+}
 
-    if (!cls) {
-        return null;
-    }
+export async function putAssignment(classid: string, id: number, assignmentData: Partial<EntityDTO<Assignment>>): Promise<AssignmentDTO> {
+    const assignment = await fetchAssignment(classid, id);
+
+    await putObject<Assignment>(assignment, assignmentData, getAssignmentRepository());
+
+    return mapToAssignmentDTO(assignment);
+}
+
+export async function deleteAssignment(classid: string, id: number): Promise<AssignmentDTO> {
+    const assignment = await fetchAssignment(classid, id);
+    const cls = await fetchClass(classid);
 
     const assignmentRepository = getAssignmentRepository();
-    const assignment = await assignmentRepository.findByClassAndId(cls, id);
-
-    if (!assignment) {
-        return null;
-    }
+    await assignmentRepository.deleteByClassAndId(cls, id);
 
     return mapToAssignmentDTO(assignment);
 }
@@ -68,19 +88,7 @@ export async function getAssignmentsSubmissions(
     assignmentNumber: number,
     full: boolean
 ): Promise<SubmissionDTO[] | SubmissionDTOId[]> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classid);
-
-    if (!cls) {
-        return [];
-    }
-
-    const assignmentRepository = getAssignmentRepository();
-    const assignment = await assignmentRepository.findByClassAndId(cls, assignmentNumber);
-
-    if (!assignment) {
-        return [];
-    }
+    const assignment = await fetchAssignment(classid, assignmentNumber);
 
     const groupRepository = getGroupRepository();
     const groups = await groupRepository.findAllGroupsForAssignment(assignment);
@@ -94,3 +102,16 @@ export async function getAssignmentsSubmissions(
 
     return submissions.map(mapToSubmissionDTOId);
 }
+
+export async function getAssignmentsQuestions(classid: string, assignmentNumber: number, full: boolean): Promise<QuestionDTO[] | QuestionId[]> {
+    const assignment = await fetchAssignment(classid, assignmentNumber);
+
+    const questionRepository = getQuestionRepository();
+    const questions = await questionRepository.findAllByAssignment(assignment);
+
+    if (full) {
+        return questions.map(mapToQuestionDTO);
+    }
+
+    return questions.map(mapToQuestionDTO);
+}
diff --git a/backend/src/services/classes.ts b/backend/src/services/classes.ts
index 754277cf..1f197b2a 100644
--- a/backend/src/services/classes.ts
+++ b/backend/src/services/classes.ts
@@ -1,22 +1,25 @@
-import { getClassRepository, getStudentRepository, getTeacherInvitationRepository, getTeacherRepository } from '../data/repositories.js';
+import { getClassRepository, getTeacherInvitationRepository } from '../data/repositories.js';
 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';
+import { fetchTeacher } from './teachers.js';
+import { fetchStudent } from './students.js';
+import { TeacherDTO } from '@dwengo-1/common/interfaces/teacher';
+import { mapToTeacherDTO } from '../interfaces/teacher.js';
+import { EntityDTO } from '@mikro-orm/core';
+import { putObject } from './service-helper.js';
 
-const logger = getLogger();
-
-export async function fetchClass(classId: string): Promise<Class> {
+export async function fetchClass(classid: string): Promise<Class> {
     const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classId);
+    const cls = await classRepository.findById(classid);
 
     if (!cls) {
-        throw new NotFoundException('Class with id not found');
+        throw new NotFoundException('Class not found');
     }
 
     return cls;
@@ -24,11 +27,7 @@ export async function fetchClass(classId: string): Promise<Class> {
 
 export async function getAllClasses(full: boolean): Promise<ClassDTO[] | string[]> {
     const classRepository = getClassRepository();
-    const classes = await classRepository.find({}, { populate: ['students', 'teachers'] });
-
-    if (!classes) {
-        return [];
-    }
+    const classes = await classRepository.findAll({ populate: ['students', 'teachers'] });
 
     if (full) {
         return classes.map(mapToClassDTO);
@@ -36,74 +35,71 @@ export async function getAllClasses(full: boolean): Promise<ClassDTO[] | string[
     return classes.map((cls) => cls.classId!);
 }
 
-export async function createClass(classData: ClassDTO): Promise<ClassDTO | null> {
-    const teacherRepository = getTeacherRepository();
-    const teacherUsernames = classData.teachers || [];
-    const teachers = (await Promise.all(teacherUsernames.map(async (id) => teacherRepository.findByUsername(id)))).filter(
-        (teacher) => teacher !== null
-    );
-
-    const studentRepository = getStudentRepository();
-    const studentUsernames = classData.students || [];
-    const students = (await Promise.all(studentUsernames.map(async (id) => studentRepository.findByUsername(id)))).filter(
-        (student) => student !== null
-    );
-
-    const classRepository = getClassRepository();
-
-    try {
-        const newClass = classRepository.create({
-            displayName: classData.displayName,
-            teachers: teachers,
-            students: students,
-        });
-        await classRepository.save(newClass);
-
-        return mapToClassDTO(newClass);
-    } catch (e) {
-        logger.error(e);
-        return null;
-    }
+export async function getClass(classId: string): Promise<ClassDTO> {
+    const cls = await fetchClass(classId);
+    return mapToClassDTO(cls);
 }
 
-export async function getClass(classId: string): Promise<ClassDTO | null> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classId);
+export async function createClass(classData: ClassDTO): Promise<ClassDTO> {
+    const teacherUsernames = classData.teachers || [];
+    const teachers = await Promise.all(teacherUsernames.map(async (id) => fetchTeacher(id)));
 
-    if (!cls) {
-        return null;
-    }
+    const studentUsernames = classData.students || [];
+    const students = await Promise.all(studentUsernames.map(async (id) => fetchStudent(id)));
+
+    const classRepository = getClassRepository();
+    const newClass = classRepository.create({
+        displayName: classData.displayName,
+        teachers: teachers,
+        students: students,
+    });
+    await classRepository.save(newClass, { preventOverwrite: true });
+
+    return mapToClassDTO(newClass);
+}
+
+export async function putClass(classId: string, classData: Partial<EntityDTO<Class>>): Promise<ClassDTO> {
+    const cls = await fetchClass(classId);
+
+    await putObject<Class>(cls, classData, getClassRepository());
 
     return mapToClassDTO(cls);
 }
 
-async function fetchClassStudents(classId: string): Promise<StudentDTO[]> {
+export async function deleteClass(classId: string): Promise<ClassDTO> {
+    const cls = await fetchClass(classId);
+
     const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classId);
+    await classRepository.deleteById(classId);
 
-    if (!cls) {
-        return [];
+    return mapToClassDTO(cls);
+}
+
+export async function getClassStudents(classId: string, full: boolean): Promise<StudentDTO[] | string[]> {
+    const cls = await fetchClass(classId);
+
+    if (full) {
+        return cls.students.map(mapToStudentDTO);
     }
+    return cls.students.map((student) => student.username);
+}
 
+export async function getClassStudentsDTO(classId: string): Promise<StudentDTO[]> {
+    const cls = await fetchClass(classId);
     return cls.students.map(mapToStudentDTO);
 }
 
-export async function getClassStudents(classId: string): Promise<StudentDTO[]> {
-    return await fetchClassStudents(classId);
-}
+export async function getClassTeachers(classId: string, full: boolean): Promise<TeacherDTO[] | string[]> {
+    const cls = await fetchClass(classId);
 
-export async function getClassStudentsIds(classId: string): Promise<string[]> {
-    const students: StudentDTO[] = await fetchClassStudents(classId);
-    return students.map((student) => student.username);
+    if (full) {
+        return cls.teachers.map(mapToTeacherDTO);
+    }
+    return cls.teachers.map((student) => student.username);
 }
 
 export async function getClassTeacherInvitations(classId: string, full: boolean): Promise<TeacherInvitationDTO[]> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classId);
-
-    if (!cls) {
-        return [];
-    }
+    const cls = await fetchClass(classId);
 
     const teacherInvitationRepository = getTeacherInvitationRepository();
     const invitations = await teacherInvitationRepository.findAllInvitationsForClass(cls);
@@ -114,3 +110,41 @@ export async function getClassTeacherInvitations(classId: string, full: boolean)
 
     return invitations.map(mapToTeacherInvitationDTOIds);
 }
+
+export async function deleteClassStudent(classId: string, username: string): Promise<ClassDTO> {
+    const cls = await fetchClass(classId);
+
+    const newStudents = { students: cls.students.filter((student) => student.username !== username) };
+    await putObject<Class>(cls, newStudents, getClassRepository());
+
+    return mapToClassDTO(cls);
+}
+
+export async function deleteClassTeacher(classId: string, username: string): Promise<ClassDTO> {
+    const cls = await fetchClass(classId);
+
+    const newTeachers = { teachers: cls.teachers.filter((teacher) => teacher.username !== username) };
+    await putObject<Class>(cls, newTeachers, getClassRepository());
+
+    return mapToClassDTO(cls);
+}
+
+export async function addClassStudent(classId: string, username: string): Promise<ClassDTO> {
+    const cls = await fetchClass(classId);
+    const newStudent = await fetchStudent(username);
+
+    const newStudents = { students: [...cls.students, newStudent] };
+    await putObject<Class>(cls, newStudents, getClassRepository());
+
+    return mapToClassDTO(cls);
+}
+
+export async function addClassTeacher(classId: string, username: string): Promise<ClassDTO> {
+    const cls = await fetchClass(classId);
+    const newTeacher = await fetchTeacher(username);
+
+    const newTeachers = { teachers: [...cls.teachers, newTeacher] };
+    await putObject<Class>(cls, newTeachers, getClassRepository());
+
+    return mapToClassDTO(cls);
+}
diff --git a/backend/src/services/groups.ts b/backend/src/services/groups.ts
index 346c1ee1..95b1b7d4 100644
--- a/backend/src/services/groups.ts
+++ b/backend/src/services/groups.ts
@@ -1,105 +1,90 @@
-import {
-    getAssignmentRepository,
-    getClassRepository,
-    getGroupRepository,
-    getStudentRepository,
-    getSubmissionRepository,
-} from '../data/repositories.js';
+import { EntityDTO } from '@mikro-orm/core';
+import { getGroupRepository, getStudentRepository, getSubmissionRepository } from '../data/repositories.js';
 import { Group } from '../entities/assignments/group.entity.js';
 import { mapToGroupDTO, mapToGroupDTOId } from '../interfaces/group.js';
 import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
 import { GroupDTO } from '@dwengo-1/common/interfaces/group';
 import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
-import { getLogger } from '../logging/initalize.js';
+import { fetchAssignment } from './assignments.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
+import { putObject } from './service-helper.js';
 
-export async function getGroup(classId: string, assignmentNumber: number, groupNumber: number, full: boolean): Promise<GroupDTO | null> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classId);
-
-    if (!cls) {
-        return null;
-    }
-
-    const assignmentRepository = getAssignmentRepository();
-    const assignment = await assignmentRepository.findByClassAndId(cls, assignmentNumber);
-
-    if (!assignment) {
-        return null;
-    }
+export async function fetchGroup(classId: string, assignmentNumber: number, groupNumber: number): Promise<Group> {
+    const assignment = await fetchAssignment(classId, assignmentNumber);
 
     const groupRepository = getGroupRepository();
     const group = await groupRepository.findByAssignmentAndGroupNumber(assignment, groupNumber);
 
     if (!group) {
-        return null;
+        throw new NotFoundException('Could not find group');
     }
 
-    if (full) {
-        return mapToGroupDTO(group);
-    }
-
-    return mapToGroupDTOId(group);
+    return group;
 }
 
-export async function createGroup(groupData: GroupDTO, classid: string, assignmentNumber: number): Promise<Group | null> {
+export async function getGroup(classId: string, assignmentNumber: number, groupNumber: number): Promise<GroupDTO> {
+    const group = await fetchGroup(classId, assignmentNumber, groupNumber);
+    return mapToGroupDTO(group);
+}
+
+export async function putGroup(
+    classId: string,
+    assignmentNumber: number,
+    groupNumber: number,
+    groupData: Partial<EntityDTO<Group>>
+): Promise<GroupDTO> {
+    const group = await fetchGroup(classId, assignmentNumber, groupNumber);
+
+    await putObject<Group>(group, groupData, getGroupRepository());
+
+    return mapToGroupDTO(group);
+}
+
+export async function deleteGroup(classId: string, assignmentNumber: number, groupNumber: number): Promise<GroupDTO> {
+    const group = await fetchGroup(classId, assignmentNumber, groupNumber);
+    const assignment = await fetchAssignment(classId, assignmentNumber);
+
+    const groupRepository = getGroupRepository();
+    await groupRepository.deleteByAssignmentAndGroupNumber(assignment, groupNumber);
+
+    return mapToGroupDTO(group);
+}
+
+export async function getExistingGroupFromGroupDTO(groupData: GroupDTO): Promise<Group> {
+    const classId = typeof groupData.class === 'string' ? groupData.class : groupData.class.id;
+    const assignmentNumber = typeof groupData.assignment === 'number' ? groupData.assignment : groupData.assignment.id;
+    const groupNumber = groupData.groupNumber;
+
+    return await fetchGroup(classId, assignmentNumber, groupNumber);
+}
+
+export async function createGroup(groupData: GroupDTO, classid: string, assignmentNumber: number): Promise<GroupDTO> {
     const studentRepository = getStudentRepository();
 
-    const memberUsernames = (groupData.members as string[]) || []; // TODO check if groupdata.members is a list
+    const memberUsernames = (groupData.members as string[]) || [];
     const members = (await Promise.all([...memberUsernames].map(async (id) => studentRepository.findByUsername(id)))).filter(
         (student) => student !== null
     );
 
-    getLogger().debug(members);
-
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classid);
-
-    if (!cls) {
-        return null;
-    }
-
-    const assignmentRepository = getAssignmentRepository();
-    const assignment = await assignmentRepository.findByClassAndId(cls, assignmentNumber);
-
-    if (!assignment) {
-        return null;
-    }
+    const assignment = await fetchAssignment(classid, assignmentNumber);
 
     const groupRepository = getGroupRepository();
-    try {
-        const newGroup = groupRepository.create({
-            assignment: assignment,
-            members: members,
-        });
-        await groupRepository.save(newGroup);
+    const newGroup = groupRepository.create({
+        assignment: assignment,
+        members: members,
+    });
+    await groupRepository.save(newGroup);
 
-        return newGroup;
-    } catch (e) {
-        getLogger().error(e);
-        return null;
-    }
+    return mapToGroupDTO(newGroup);
 }
 
 export async function getAllGroups(classId: string, assignmentNumber: number, full: boolean): Promise<GroupDTO[]> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classId);
-
-    if (!cls) {
-        return [];
-    }
-
-    const assignmentRepository = getAssignmentRepository();
-    const assignment = await assignmentRepository.findByClassAndId(cls, assignmentNumber);
-
-    if (!assignment) {
-        return [];
-    }
+    const assignment = await fetchAssignment(classId, assignmentNumber);
 
     const groupRepository = getGroupRepository();
     const groups = await groupRepository.findAllGroupsForAssignment(assignment);
 
     if (full) {
-        getLogger().debug({ full: full, groups: groups });
         return groups.map(mapToGroupDTO);
     }
 
@@ -112,26 +97,7 @@ export async function getGroupSubmissions(
     groupNumber: number,
     full: boolean
 ): Promise<SubmissionDTO[] | SubmissionDTOId[]> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classId);
-
-    if (!cls) {
-        return [];
-    }
-
-    const assignmentRepository = getAssignmentRepository();
-    const assignment = await assignmentRepository.findByClassAndId(cls, assignmentNumber);
-
-    if (!assignment) {
-        return [];
-    }
-
-    const groupRepository = getGroupRepository();
-    const group = await groupRepository.findByAssignmentAndGroupNumber(assignment, groupNumber);
-
-    if (!group) {
-        return [];
-    }
+    const group = await fetchGroup(classId, assignmentNumber, groupNumber);
 
     const submissionRepository = getSubmissionRepository();
     const submissions = await submissionRepository.findAllSubmissionsForGroup(group);
diff --git a/backend/src/services/service-helper.ts b/backend/src/services/service-helper.ts
new file mode 100644
index 00000000..641fada4
--- /dev/null
+++ b/backend/src/services/service-helper.ts
@@ -0,0 +1,20 @@
+import { EntityDTO, FromEntityType } from '@mikro-orm/core';
+import { DwengoEntityRepository } from '../data/dwengo-entity-repository';
+
+/**
+ * Utility function to perform an PUT on an object.
+ *
+ * @param object The object that needs to be changed
+ * @param data The datafields and their values that will be updated
+ * @param repo The repository on which this action needs to be performed
+ *
+ * @returns Nothing.
+ */
+export async function putObject<T extends object>(
+    object: T,
+    data: Partial<EntityDTO<FromEntityType<T>>>,
+    repo: DwengoEntityRepository<T>
+): Promise<void> {
+    repo.assign(object, data);
+    await repo.getEntityManager().flush();
+}
diff --git a/backend/src/services/students.ts b/backend/src/services/students.ts
index dc40e468..6cfbbd5b 100644
--- a/backend/src/services/students.ts
+++ b/backend/src/services/students.ts
@@ -23,6 +23,7 @@ import { GroupDTO } from '@dwengo-1/common/interfaces/group';
 import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
 import { QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
 import { ClassJoinRequestDTO } from '@dwengo-1/common/interfaces/class-join-request';
+import { ConflictException } from '../exceptions/conflict-exception.js';
 
 export async function getAllStudents(full: boolean): Promise<StudentDTO[] | string[]> {
     const studentRepository = getStudentRepository();
@@ -135,6 +136,10 @@ export async function createClassJoinRequest(username: string, classId: string):
     const student = await fetchStudent(username); // Throws error if student not found
     const cls = await fetchClass(classId);
 
+    if (cls.students.contains(student)) {
+        throw new ConflictException('Student already in this class');
+    }
+
     const request = mapToStudentRequest(student, cls);
     await requestRepo.save(request, { preventOverwrite: true });
     return mapToStudentRequestDTO(request);
diff --git a/backend/src/services/submissions.ts b/backend/src/services/submissions.ts
index 1d8a7874..c7daff74 100644
--- a/backend/src/services/submissions.ts
+++ b/backend/src/services/submissions.ts
@@ -1,57 +1,51 @@
 import { getSubmissionRepository } from '../data/repositories.js';
 import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
 import { mapToSubmission, mapToSubmissionDTO } from '../interfaces/submission.js';
 import { SubmissionDTO } from '@dwengo-1/common/interfaces/submission';
-import { Language } from '@dwengo-1/common/util/language';
-
-export async function getSubmission(
-    learningObjectHruid: string,
-    language: Language,
-    version: number,
-    submissionNumber: number
-): Promise<SubmissionDTO | null> {
-    const loId = new LearningObjectIdentifier(learningObjectHruid, language, version);
+import { fetchStudent } from './students.js';
+import { getExistingGroupFromGroupDTO } from './groups.js';
+import { Submission } from '../entities/assignments/submission.entity.js';
 
+export async function fetchSubmission(loId: LearningObjectIdentifier, submissionNumber: number): Promise<Submission> {
     const submissionRepository = getSubmissionRepository();
     const submission = await submissionRepository.findSubmissionByLearningObjectAndSubmissionNumber(loId, submissionNumber);
 
     if (!submission) {
-        return null;
+        throw new NotFoundException('Could not find submission');
     }
 
-    return mapToSubmissionDTO(submission);
-}
-
-export async function createSubmission(submissionDTO: SubmissionDTO): Promise<SubmissionDTO | null> {
-    const submissionRepository = getSubmissionRepository();
-    const submission = mapToSubmission(submissionDTO);
-
-    try {
-        const newSubmission = submissionRepository.create(submission);
-        await submissionRepository.save(newSubmission);
-    } catch (_) {
-        return null;
-    }
-
-    return mapToSubmissionDTO(submission);
-}
-
-export async function deleteSubmission(
-    learningObjectHruid: string,
-    language: Language,
-    version: number,
-    submissionNumber: number
-): Promise<SubmissionDTO | null> {
-    const submissionRepository = getSubmissionRepository();
-
-    const submission = getSubmission(learningObjectHruid, language, version, submissionNumber);
-
-    if (!submission) {
-        return null;
-    }
-
-    const loId = new LearningObjectIdentifier(learningObjectHruid, language, version);
-    await submissionRepository.deleteSubmissionByLearningObjectAndSubmissionNumber(loId, submissionNumber);
-
     return submission;
 }
+
+export async function getSubmission(loId: LearningObjectIdentifier, submissionNumber: number): Promise<SubmissionDTO> {
+    const submission = await fetchSubmission(loId, submissionNumber);
+    return mapToSubmissionDTO(submission);
+}
+
+export async function getAllSubmissions(loId: LearningObjectIdentifier): Promise<SubmissionDTO[]> {
+    const submissionRepository = getSubmissionRepository();
+    const submissions = await submissionRepository.findByLearningObject(loId);
+
+    return submissions.map(mapToSubmissionDTO);
+}
+
+export async function createSubmission(submissionDTO: SubmissionDTO): Promise<SubmissionDTO> {
+    const submitter = await fetchStudent(submissionDTO.submitter.username);
+    const group = submissionDTO.group ? await getExistingGroupFromGroupDTO(submissionDTO.group) : undefined;
+
+    const submissionRepository = getSubmissionRepository();
+    const submission = mapToSubmission(submissionDTO, submitter, group);
+    await submissionRepository.save(submission);
+
+    return mapToSubmissionDTO(submission);
+}
+
+export async function deleteSubmission(loId: LearningObjectIdentifier, submissionNumber: number): Promise<SubmissionDTO> {
+    const submission = await fetchSubmission(loId, submissionNumber);
+
+    const submissionRepository = getSubmissionRepository();
+    await submissionRepository.deleteSubmissionByLearningObjectAndSubmissionNumber(loId, submissionNumber);
+
+    return mapToSubmissionDTO(submission);
+}
diff --git a/backend/src/services/teachers.ts b/backend/src/services/teachers.ts
index 1b7643fb..e6596f9e 100644
--- a/backend/src/services/teachers.ts
+++ b/backend/src/services/teachers.ts
@@ -22,13 +22,14 @@ 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 { addClassStudent, fetchClass, getClassStudentsDTO } 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 { ClassJoinRequestDTO } from '@dwengo-1/common/interfaces/class-join-request';
 import { ClassJoinRequestStatus } from '@dwengo-1/common/util/class-join-request';
+import { ConflictException } from '../exceptions/conflict-exception.js';
 
 export async function getAllTeachers(full: boolean): Promise<TeacherDTO[] | string[]> {
     const teacherRepository: TeacherRepository = getTeacherRepository();
@@ -99,10 +100,12 @@ export async function getStudentsByTeacher(username: string, full: boolean): Pro
 
     const classIds: string[] = classes.map((cls) => cls.id);
 
-    const students: StudentDTO[] = (await Promise.all(classIds.map(async (id) => getClassStudents(id)))).flat();
+    const students: StudentDTO[] = (await Promise.all(classIds.map(async (username) => await getClassStudentsDTO(username)))).flat();
+
     if (full) {
         return students;
     }
+
     return students.map((student) => student.username);
 }
 
@@ -143,13 +146,12 @@ export async function getJoinRequestsByClass(classId: string): Promise<ClassJoin
 
 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);
+    const cls = await fetchClass(classId);
 
-    if (!cls) {
-        throw new NotFoundException('Class not found');
+    if (cls.students.contains(student)) {
+        throw new ConflictException('Student already in this class');
     }
 
     const request: ClassJoinRequest | null = await requestRepo.findByStudentAndClass(student, cls);
@@ -158,8 +160,14 @@ export async function updateClassJoinRequestStatus(studentUsername: string, clas
         throw new NotFoundException('Join request not found');
     }
 
-    request.status = accepted ? ClassJoinRequestStatus.Accepted : ClassJoinRequestStatus.Declined;
+    request.status = ClassJoinRequestStatus.Declined;
+
+    if (accepted) {
+        request.status = ClassJoinRequestStatus.Accepted;
+        await addClassStudent(classId, studentUsername);
+    }
 
     await requestRepo.save(request);
+
     return mapToStudentRequestDTO(request);
 }
diff --git a/backend/tests/controllers/students.test.ts b/backend/tests/controllers/students.test.ts
index 18331f2d..aca29de1 100644
--- a/backend/tests/controllers/students.test.ts
+++ b/backend/tests/controllers/students.test.ts
@@ -198,15 +198,34 @@ describe('Student controllers', () => {
         );
     });
 
-    it('Create join request', async () => {
+    it('Create and delete join request', async () => {
         req = {
-            params: { username: 'Noordkaap' },
+            params: { username: 'TheDoors' },
             body: { classId: '34d484a1-295f-4e9f-bfdc-3e7a23d86a89' },
         };
 
         await createStudentRequestHandler(req as Request, res as Response);
 
         expect(jsonMock).toHaveBeenCalledWith(expect.objectContaining({ request: expect.anything() }));
+
+        req = {
+            params: { username: 'TheDoors', classId: '34d484a1-295f-4e9f-bfdc-3e7a23d86a89' },
+        };
+
+        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);
+    });
+
+    it('Create join request student already in class error', async () => {
+        req = {
+            params: { username: 'Noordkaap' },
+            body: { classId: '34d484a1-295f-4e9f-bfdc-3e7a23d86a89' },
+        };
+
+        await expect(async () => createStudentRequestHandler(req as Request, res as Response)).rejects.toThrow(ConflictException);
     });
 
     it('Create join request duplicate', async () => {
@@ -217,16 +236,4 @@ describe('Student controllers', () => {
 
         await expect(async () => createStudentRequestHandler(req as Request, res as Response)).rejects.toThrow(ConflictException);
     });
-
-    it('Delete join request', async () => {
-        req = {
-            params: { username: 'Noordkaap', classId: '34d484a1-295f-4e9f-bfdc-3e7a23d86a89' },
-        };
-
-        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
index cdcb6229..a73a79a5 100644
--- a/backend/tests/controllers/teachers.test.ts
+++ b/backend/tests/controllers/teachers.test.ts
@@ -16,6 +16,7 @@ import { BadRequestException } from '../../src/exceptions/bad-request-exception.
 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';
+import { getClassHandler } from '../../src/controllers/classes';
 
 describe('Teacher controllers', () => {
     let req: Partial<Request>;
@@ -168,7 +169,6 @@ describe('Teacher controllers', () => {
 
     it('Get join requests by class', async () => {
         req = {
-            query: { username: 'LimpBizkit' },
             params: { classId: '34d484a1-295f-4e9f-bfdc-3e7a23d86a89' },
         };
 
@@ -183,8 +183,7 @@ describe('Teacher controllers', () => {
 
     it('Update join request status', async () => {
         req = {
-            query: { username: 'LimpBizkit', studentUsername: 'PinkFloyd' },
-            params: { classId: '34d484a1-295f-4e9f-bfdc-3e7a23d86a89' },
+            params: { classId: '34d484a1-295f-4e9f-bfdc-3e7a23d86a89', studentUsername: 'PinkFloyd' },
             body: { accepted: 'true' },
         };
 
@@ -200,5 +199,13 @@ describe('Teacher controllers', () => {
 
         const status: boolean = jsonMock.mock.lastCall?.[0].requests[0].status;
         expect(status).toBeTruthy();
+
+        req = {
+            params: { id: '34d484a1-295f-4e9f-bfdc-3e7a23d86a89' },
+        };
+
+        await getClassHandler(req as Request, res as Response);
+        const students: string[] = jsonMock.mock.lastCall?.[0].class.students;
+        expect(students).contains('PinkFloyd');
     });
 });
diff --git a/common/src/interfaces/assignment.ts b/common/src/interfaces/assignment.ts
index 8ad1649b..5cb8feff 100644
--- a/common/src/interfaces/assignment.ts
+++ b/common/src/interfaces/assignment.ts
@@ -2,7 +2,7 @@ import { GroupDTO } from './group';
 
 export interface AssignmentDTO {
     id: number;
-    class: string; // Id of class 'within'
+    within: string;
     title: string;
     description: string;
     learningPath: string;
diff --git a/common/src/interfaces/class.ts b/common/src/interfaces/class.ts
index c35c2dfc..d71e15e6 100644
--- a/common/src/interfaces/class.ts
+++ b/common/src/interfaces/class.ts
@@ -3,5 +3,4 @@ export interface ClassDTO {
     displayName: string;
     teachers: string[];
     students: string[];
-    joinRequests: string[];
 }
diff --git a/common/src/interfaces/group.ts b/common/src/interfaces/group.ts
index ca95770a..742f2c75 100644
--- a/common/src/interfaces/group.ts
+++ b/common/src/interfaces/group.ts
@@ -1,7 +1,9 @@
 import { AssignmentDTO } from './assignment';
+import { ClassDTO } from './class';
 import { StudentDTO } from './student';
 
 export interface GroupDTO {
+    class: string | ClassDTO;
     assignment: number | AssignmentDTO;
     groupNumber: number;
     members: string[] | StudentDTO[];
diff --git a/frontend/src/controllers/assignments.ts b/frontend/src/controllers/assignments.ts
index 59ea2428..a66f8e84 100644
--- a/frontend/src/controllers/assignments.ts
+++ b/frontend/src/controllers/assignments.ts
@@ -33,6 +33,10 @@ export class AssignmentController extends BaseController {
         return this.delete<AssignmentResponse>(`/${num}`);
     }
 
+    async updateAssignment(num: number, data: Partial<AssignmentDTO>): Promise<AssignmentResponse> {
+        return this.put<AssignmentResponse>(`/${num}`, data);
+    }
+
     async getSubmissions(assignmentNumber: number, full = true): Promise<SubmissionsResponse> {
         return this.get<SubmissionsResponse>(`/${assignmentNumber}/submissions`, { full });
     }
diff --git a/frontend/src/controllers/classes.ts b/frontend/src/controllers/classes.ts
index c2a634eb..03e3f560 100644
--- a/frontend/src/controllers/classes.ts
+++ b/frontend/src/controllers/classes.ts
@@ -3,6 +3,7 @@ import type { ClassDTO } from "@dwengo-1/common/interfaces/class";
 import type { StudentsResponse } from "./students";
 import type { AssignmentsResponse } from "./assignments";
 import type { TeacherInvitationDTO } from "@dwengo-1/common/interfaces/teacher-invitation";
+import type { TeachersResponse } from "@/controllers/teachers.ts";
 
 export interface ClassesResponse {
     classes: ClassDTO[] | string[];
@@ -41,10 +42,34 @@ export class ClassController extends BaseController {
         return this.delete<ClassResponse>(`/${id}`);
     }
 
+    async updateClass(id: string, data: Partial<ClassDTO>): Promise<ClassResponse> {
+        return this.put<ClassResponse>(`/${id}`, data);
+    }
+
     async getStudents(id: string, full = true): Promise<StudentsResponse> {
         return this.get<StudentsResponse>(`/${id}/students`, { full });
     }
 
+    async addStudent(id: string, username: string): Promise<ClassResponse> {
+        return this.post<ClassResponse>(`/${id}/students`, { username });
+    }
+
+    async deleteStudent(id: string, username: string): Promise<ClassResponse> {
+        return this.delete<ClassResponse>(`/${id}/students/${username}`);
+    }
+
+    async getTeachers(id: string, full = true): Promise<TeachersResponse> {
+        return this.get<TeachersResponse>(`/${id}/teachers`, { full });
+    }
+
+    async addTeacher(id: string, username: string): Promise<ClassResponse> {
+        return this.post<ClassResponse>(`/${id}/teachers`, { username });
+    }
+
+    async deleteTeacher(id: string, username: string): Promise<ClassResponse> {
+        return this.delete<ClassResponse>(`/${id}/teachers/${username}`);
+    }
+
     async getTeacherInvitations(id: string, full = true): Promise<TeacherInvitationsResponse> {
         return this.get<TeacherInvitationsResponse>(`/${id}/teacher-invitations`, { full });
     }
diff --git a/frontend/src/controllers/groups.ts b/frontend/src/controllers/groups.ts
index 05192636..de6592b5 100644
--- a/frontend/src/controllers/groups.ts
+++ b/frontend/src/controllers/groups.ts
@@ -32,6 +32,10 @@ export class GroupController extends BaseController {
         return this.delete<GroupResponse>(`/${num}`);
     }
 
+    async updateGroup(num: number, data: Partial<GroupDTO>): Promise<GroupResponse> {
+        return this.put<GroupResponse>(`/${num}`, data);
+    }
+
     async getSubmissions(groupNumber: number, full = true): Promise<SubmissionsResponse> {
         return this.get<SubmissionsResponse>(`/${groupNumber}/submissions`, { full });
     }