The companion legislation (the Developmental Disabilities Assistance and Bill of Rights Act) also supported the least restrictive environment (LRE) principle. Children who were not currently receiving a public education were to get first priority in the use of federal funds by states. The regulations enacting P. L. 94-142 became effective in 1977. States were initially given until 1978 to implement the regulations but this was later extended to 1981.
One of the major impacts of P. L. 94-142 was to increasingly prevent the institutionalization of children. One provision of P. L. 94-142 required states to establish priorities for providing a free appropriate education to all children [with developmental disabilities]… first with respect to children who are not receiving an education, and second with respect to children, within each disability, with most severe disabilities who are receiving an inadequate education…