Why are children with physical disabilities and other health impairment placed in self contained classes with children who have mental retardation?

I think right now they place children with "disabilities" whether it's physical or mental together most likely because they just don't have the budget or space maybe to put them in separate rooms.

Their are some schools who do place well bodied students who might have mental disabilities in rooms with those who share the same mental capacity.

Since well minded students who might have physical or "other health impairments" are mentally aware and capable of learning on a much higher and quicker level than those of their mentally impaired peers. It just makes more sense to separate them for the sake of those who will learn on different levels than the mentally retarded.

Hopefully the school system will catch up.