diff --git a/packages/server/src/module/quiz/quizzes/entities/quiz.entity.ts b/packages/server/src/module/quiz/quizzes/entities/quiz.entity.ts
index 56a765c..30f7f02 100644
--- a/packages/server/src/module/quiz/quizzes/entities/quiz.entity.ts
+++ b/packages/server/src/module/quiz/quizzes/entities/quiz.entity.ts
@@ -3,7 +3,7 @@ import { QuizType } from '../utils/quiz-type.enum';
 import { Choice } from './choice.entity';
 import { Class } from './class.entity';
 
-@Entity()
+@Entity('quiz')
 export class Quiz {
   @PrimaryGeneratedColumn()
   id: number;
@@ -15,10 +15,10 @@ export class Quiz {
   content: string;
 
   @Column({
-      name: 'quiz_type',
-      type: 'enum',
-      enum: QuizType,
-      default: QuizType.TF,
+    name: 'quiz_type',
+    type: 'enum',
+    enum: QuizType,
+    default: QuizType.TF,
   })
   quizType: QuizType;
 
@@ -29,18 +29,18 @@ export class Quiz {
   point: number;
 
   @Column()
-  position: number
+  position: number;
 
   @Column({ name: 'created_at' })
   createdAt: Date;
 
-  @OneToMany(() => Choice, choice => choice.quiz, {
+  @OneToMany(() => Choice, (choice) => choice.quiz, {
     cascade: true,
-    eager: false
+    eager: false,
   })
   choices: Choice[];
 
-  @ManyToOne(() => Class, cls => cls.quizzes)
-  @JoinColumn({ name: 'class_id' })
+  @ManyToOne(() => Class, (cls) => cls.quizzes)
+  @JoinColumn([{ name: 'class_id', referencedColumnName: 'id' }])
   class: Class;
-}
\ No newline at end of file
+}
diff --git a/packages/server/src/module/quiz/quizzes/quiz.service.ts b/packages/server/src/module/quiz/quizzes/quiz.service.ts
index 39f9dc8..721f1c5 100644
--- a/packages/server/src/module/quiz/quizzes/quiz.service.ts
+++ b/packages/server/src/module/quiz/quizzes/quiz.service.ts
@@ -106,6 +106,11 @@ export class QuizService {
   }
 
   async deleteClass(id: number): Promise<void> {
-    await this.classRepository.deleteWithRelations(id);
+    return this.dataSource.transaction(async (manager) => {
+      await this.classRepository.findClassById(id);
+      await this.choiceRepository.deleteByClassId(id, manager);
+      await this.quizRepository.deleteByClassId(id, manager);
+      await this.classRepository.delete(id, manager);
+    });
   }
 }
diff --git a/packages/server/src/module/quiz/quizzes/repositories/choice.repository.ts b/packages/server/src/module/quiz/quizzes/repositories/choice.repository.ts
index de889c8..20171b3 100644
--- a/packages/server/src/module/quiz/quizzes/repositories/choice.repository.ts
+++ b/packages/server/src/module/quiz/quizzes/repositories/choice.repository.ts
@@ -11,11 +11,7 @@ export class ChoiceRepository {
     private readonly repository: Repository<Choice>,
   ) {}
 
-  async create(
-    quizId: number,
-    choiceData: CreateChoiceRequestDto,
-    manager?: EntityManager,
-  ): Promise<Choice> {
+  async create(quizId: number, choiceData: CreateChoiceRequestDto): Promise<Choice> {
     const { content, isCorrect, position } = choiceData;
     const choiceEntity = this.repository.create({
       quizId,
@@ -72,12 +68,10 @@ export class ChoiceRepository {
     }
   }
 
-  async deleteByQuizId(quizId: number, manager?: EntityManager): Promise<void> {
-    const repo = manager ? manager.getRepository(Choice) : this.repository;
-    try {
-      await repo.delete({ quizId });
-    } catch (error) {
-      throw new InternalServerErrorException('Failed to delete choices');
-    }
+  async deleteByClassId(classId: number, manager: EntityManager): Promise<void> {
+    await manager.query(
+      'DELETE FROM choice WHERE quiz_id IN (SELECT id FROM quiz WHERE class_id = ?)',
+      [classId],
+    );
   }
 }
diff --git a/packages/server/src/module/quiz/quizzes/repositories/class.repository.ts b/packages/server/src/module/quiz/quizzes/repositories/class.repository.ts
index 6ab4da5..b5f898e 100644
--- a/packages/server/src/module/quiz/quizzes/repositories/class.repository.ts
+++ b/packages/server/src/module/quiz/quizzes/repositories/class.repository.ts
@@ -1,6 +1,6 @@
 import { Injectable, InternalServerErrorException, NotFoundException } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
-import { DataSource, Repository } from 'typeorm';
+import { DataSource, EntityManager, Repository } from 'typeorm';
 import { Class } from '../entities/class.entity';
 
 @Injectable()
@@ -128,27 +128,7 @@ export class ClassRepository {
     }
   }
 
-  async deleteWithRelations(id: number): Promise<void> {
-    const queryRunner = this.dataSource.createQueryRunner();
-    await queryRunner.connect();
-    await queryRunner.startTransaction();
-
-    try {
-      await queryRunner.query(
-        `DELETE FROM choice WHERE quiz_id IN (SELECT id FROM quiz WHERE class_id = ?)`,
-        [id],
-      );
-
-      await queryRunner.query(`DELETE FROM quiz WHERE class_id = ?`, [id]);
-
-      await queryRunner.query(`DELETE FROM class WHERE id = ?`, [id]);
-
-      await queryRunner.commitTransaction();
-    } catch (error) {
-      await queryRunner.rollbackTransaction();
-      throw new InternalServerErrorException('Failed to delete');
-    } finally {
-      await queryRunner.release();
-    }
+  async delete(id: number, manager: EntityManager): Promise<void> {
+    await manager.delete(Class, { id });
   }
 }
diff --git a/packages/server/src/module/quiz/quizzes/repositories/quiz.repository.ts b/packages/server/src/module/quiz/quizzes/repositories/quiz.repository.ts
index cb3db41..50c0ad1 100644
--- a/packages/server/src/module/quiz/quizzes/repositories/quiz.repository.ts
+++ b/packages/server/src/module/quiz/quizzes/repositories/quiz.repository.ts
@@ -198,4 +198,8 @@ export class QuizRepository {
       await queryRunner.release();
     }
   }
+
+  async deleteByClassId(classId: number, manager: EntityManager): Promise<void> {
+    await manager.query('DELETE FROM quiz WHERE class_id = ?', [classId]);
+  }
 }