diff --git a/backend/src/services/teachers.ts b/backend/src/services/teachers.ts
index 3ebc6609..4e67d27d 100644
--- a/backend/src/services/teachers.ts
+++ b/backend/src/services/teachers.ts
@@ -22,13 +22,15 @@ 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, getClassStudentsDTO } from './classes.js';
+import {addClassStudent, fetchClass, getClassStudents, 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 {BadRequestException} from "../exceptions/bad-request-exception";
+import {ConflictException} from "../exceptions/conflict-exception";
 
 export async function getAllTeachers(full: boolean): Promise<TeacherDTO[] | string[]> {
     const teacherRepository: TeacherRepository = getTeacherRepository();
@@ -145,13 +147,12 @@ 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);
@@ -160,8 +161,14 @@ 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);
 }