Special education is under fire from full inclusionists who advocate for children with severe mental retardation and who contend that special education settings are immoral dumping grounds for children deemed "unteachable." Other advocates of inclusion focus on the invalidity of disability categories, tests, and instructional services which, in the case of students with learning disabilities, ignores evidence that these students have learning needs substantially different from other students. Special education is special because of its unique resources, its impact on student performance, and the effective teaching practices that mediate between resources and performance. Special education emphasizes individualized instruction, smaller classes, and more highly trained teachers and is supported by large amounts of research and development. Scholarly reviews of the literature, time-series research, and teacher and parent surveys offer evidence of the success of special education in promoting the academic achievement of certain disability groups. Successful special educators use empirically validated procedures and an intensive, data-based focus on individual students, such as curriculum-based measurement. Many such practices validated by special educators do not transfer easily to mainstream classrooms, where teachers have many students and often a different set of assumptions about the form and function of education. (Contains approximately 100 references.) (JDD)