The court decisions did not use "least restrictive environment," but certainly described it. The Pennsylvania settlement said:

Placement in a regular school is preferable to placement in a special school class is preferable to placement in any other type of program of education and training.

The court cases of the early 1970s that focused on institutions did use "least restrictive environment" explicitly.

Following on the court decisions, a number of federal laws between 1973 and 1975 strengthened the civil rights protections related to education.

Photos courtesy William Bronston, M.D.