diff --git a/apps/server/src/students/dto/student.dto.spec.ts b/apps/server/src/students/dto/student.dto.spec.ts
new file mode 100644
index 0000000..916514d
--- /dev/null
+++ b/apps/server/src/students/dto/student.dto.spec.ts
@@ -0,0 +1,18 @@
+import 'reflect-metadata';
+import { validate } from 'class-validator';
+import { CreateStudentDto } from './student.dto';
+
+describe('CreateStudentDto relationship boundaries', () => {
+  it('removes classId because class membership is managed by the classes API', async () => {
+    const dto = Object.assign(new CreateStudentDto(), {
+      name: '测试学生',
+      organizationId: 1,
+      classId: 9,
+    });
+
+    await validate(dto, { whitelist: true });
+
+    expect(dto).toMatchObject({ name: '测试学生', organizationId: 1 });
+    expect(dto).not.toHaveProperty('classId');
+  });
+});
diff --git a/apps/server/src/students/dto/student.dto.ts b/apps/server/src/students/dto/student.dto.ts
index 40c4bdd..bc08e95 100644
--- a/apps/server/src/students/dto/student.dto.ts
+++ b/apps/server/src/students/dto/student.dto.ts
@@ -38,9 +38,6 @@ export class CreateStudentDto {
   @IsOptional()
   @IsString()
   supervisor?: string;
-  @IsOptional()
-  @IsInt()
-  classId?: number;
 }
 
 export class UpdateStudentDto {