The condition of mental retardation has been recognized for several thousand years, particularly at the levels that would now be called severe or profound retardation. However, special education services for children with mental retardation did not begin until the early 1800s, largely through the work of French physician and educator Jean Marc Gaspard Itard. Itard claimed that students with mental retardation could be taught to perform daily living skills, like preparing meals without assistance. In the mid-1800s French-born American psychologist and doctor Edouard Séguin, who had studied with Itard, recognized that individuals with mental retardation could be taught to be more independent, especially when instructors concentrated on developing specific skills. During the 19th century, most educational services for mentally retarded students took place in residential institutions where persons with retardation were separated from the rest of society.
In the 20th century educators changed their approach to the education of students with mental retardation. Much of this change resulted from the introduction in 1905 of the Binet-Simon Scale, an intelligence test developed by French psychologists Alfred Binet and Théodore Simon. The Binet-Simon Scale provided a standard measurement of intelligence levels in children and adults. American psychologist Lewis Madison Terman later developed the Stanford-Binet intelligence test, which became the most common method used in the United States for identifying individuals with mental retardation.
During World War I (1914-1918), military psychologists developed a program for testing the intelligence of new recruits. Many young men failed the test, causing experts to recognize a far greater prevalence of mental retardation than had previously been acknowledged. Society generally recognized that special education services should be provided for mildly retarded individuals. However, for the next half century the setting for these services was as separate from regular classrooms as possible.