The job of the schools is to teach the curriculum to large numbers of students at the top of the ladder. They are trained, financed, evaluated and rewarded on their success as measured by the state and national academic standards. This includes the special education programs in schools. Special education teachers are taught to provide accommodations and modifications in the curriculum for students that struggle in the form of Individual Education Plans (IEP).
For some students, things like smaller classrooms, decreased volume in assignments and such things as extra time or repetition of curriculum in a smaller setting works to help them get what they need!