Children with severe learning disabilities and behavioral problems have to be babysat. So you commonly hire some wildly unqualified adult to follow them around and do 1-on-1 support until they age out of public school.
Yes, if the person or child is mentally disabled, then there is little that anyone can do once they've reached their maximum capacity. Then a babysitter is required and all that is really needed. However, there are other learning disabilities that can be treated by professionals and will help the child develop more normally.