Federal law requires every child must be “educated”. They even force parents to send anacephalic (born with very little brain tissue and very small heads) kids to school, who have the mental age of an young infant, and physically grow no bigger than a 4 year old. Obviously, some of the children sent to school, get no benefit from it. But there are all types of mental impairments, from the anacephalic to the high functioning autistic kids. Every parent holds out hope that their child can reach their maximum potential, but some kids are so impaired, they get nothing out of going to school.
To be more clear, kids with severe issues used to be sent to separate schools or separate classes, they now are legally forced to be in regular classes with normal kids. Not good for either group.