public static void DeleteChilds(this IRepository<School> sc, int schoolId) 
        {
            var studentsRepo = new EfRepository<Student>(new SchoolContext());

            var studentsFromSchool = studentsRepo.All().Where(x => x.School.SchoolId == schoolId).ToList();



            foreach (Student student in studentsFromSchool)
            {    
                studentsRepo.DeleteChilds(student.School.SchoolId);
                studentsRepo.Delete(student.StudentId);
            }
        }