States were required to develop and implement "child find" systems. When word got out about the availability of a public education, some parents saw they had an alternative to the physicians' recommendations to institutionalize their children. As Val Bradley comments, this had a powerful effect on the capacity of families to stay together.
If we mark progress in our field by those events that bolstered the ability of people with disabilities to remain and thrive in their communities, then the passage of the Education for All Handicapped Children's Act was probably the singularly most important piece of federal legislation. Working in family support over the years, I can't count the numbers of people I've met who were forced to place their family member in an institution because they couldn't bear up under the stress of caring for a son or daughter with disabilities for 24 hours a day – the result of the exclusion of children with disabilities from from general public school.
Basically, P. L. 94-142 guaranteed the right of children with disabilities into the public education system, not necessarily into the schools and classrooms where children without disabilities went.
Public Law 94-142 was certainly a major human rights break through. In a court decision about exclusionary zoning against group homes, the U. S. Supreme Court decision included an analysis of the history of segregation and the importance of P. L. 94-142.
"By the latter part of the 19th century and during the first decades of the new one, social views of people with disabilities underwent a radical transformation... [a] regime of state-mandated segregation and degradation soon emerged that in its virulence and bigotry rivaled, and indeed paralleled, the worse excesses of Jim Crow... Children with disabilities were categorically excluded from public schools, based on the false stereotype that all were uneducable and on the purported need to protect children [without disabilities] from them.
In 1985, the Court observed: "Prejudice, once let loose, is not easily cabined... Not until Congress enacted the Education of the Handicapped* Act were the doors of public education opened wide to children with disabilities. But most important, lengthy and continuing isolation of people with disabilities has perpetuated the ignorance, irrational fears, and stereotyping that long have plagued them."