diff --git a/apps/server/src/classes/classes.controller.spec.ts b/apps/server/src/classes/classes.controller.spec.ts
index 1c8d7e4..102a40d 100644
--- a/apps/server/src/classes/classes.controller.spec.ts
+++ b/apps/server/src/classes/classes.controller.spec.ts
@@ -1,5 +1,7 @@
+import { ValidationPipe } from '@nestjs/common';
 import { ClassesController } from './classes.controller';
 import { ClassesService } from './classes.service';
+import { QueryClassDto } from './dto/class.dto';
 import { OperationLogsService } from '../operation-logs/operation-logs.service';
 import { NotificationsService } from '../notifications/notifications.service';
 import { CaslAction, SubjectName } from '../authorization';
@@ -94,3 +96,21 @@ describe('ClassesController - class data scope', () => {
     expect(service.assertClassAccess).toHaveBeenCalledWith(21, 8, false);
   });
 });
+
+describe('QueryClassDto - query transformation', () => {
+  const pipe = new ValidationPipe({ transform: true, whitelist: true, forbidNonWhitelisted: true });
+
+  it.each([
+    ['false', false],
+    ['0', false],
+    ['true', true],
+    ['1', true],
+  ])('transforms isArchived=%s to %s', async (input, expected) => {
+    await expect(
+      pipe.transform(
+        { isArchived: input },
+        { type: 'query', metatype: QueryClassDto, data: undefined },
+      ),
+    ).resolves.toEqual({ isArchived: expected });
+  });
+});
diff --git a/apps/server/src/classes/classes.controller.ts b/apps/server/src/classes/classes.controller.ts
index 2dc8dca..547528b 100644
--- a/apps/server/src/classes/classes.controller.ts
+++ b/apps/server/src/classes/classes.controller.ts
@@ -8,6 +8,8 @@ import {
   Param,
   Query,
   UseGuards,
+  UsePipes,
+  ValidationPipe,
   Request,
   Res,
 } from '@nestjs/common';
@@ -45,6 +47,7 @@ const teacherRoleLabels: Record<string, string> = {
 };
 
 @UseGuards(JwtAuthGuard)
+@UsePipes(new ValidationPipe({ transform: true, whitelist: true, forbidNonWhitelisted: true }))
 @Controller('classes')
 export class ClassesController {
   constructor(
diff --git a/apps/server/src/classes/dto/class.dto.ts b/apps/server/src/classes/dto/class.dto.ts
index 9df9088..3d1e837 100644
--- a/apps/server/src/classes/dto/class.dto.ts
+++ b/apps/server/src/classes/dto/class.dto.ts
@@ -9,6 +9,7 @@ import {
   ArrayNotEmpty,
   ValidateNested,
   Min,
+  IsBoolean,
 } from 'class-validator';
 import { Type, Transform } from 'class-transformer';
 import { ClassType, ClassStatus, TeacherRoleType } from '../../entities';
@@ -160,6 +161,7 @@ export class QueryClassDto {
     if (value === 'false' || value === '0') return false;
     return value;
   })
+  @IsBoolean()
   isArchived?: boolean;
 }