We have that too. I'm not sure either if it's NCLB or something like ADA, but I've been told that if a parent insists that their child be mainstreamed, no matter how ill-suited, all the school system can do is mainstream that child. The school system has to provide the specialists for the child, too, like interpreters, readers or hearers for the blind or deaf, nurses, and nurses' aids (for changing diapers.) It's very expensive to do that anyway, but much, much cheaper if you can provide such specialized care and teaching at one or a few centralized schools. If you have to provide those services for each child at whatever local school to which he or she is most proximate, it gets REALLY expensive. A dozen children without bowel control would need one or two diaper changers in one CDC class, but a dozen if they are in individual classes. Plus it's rather disruptive to the class if a child needs one or two adults in attendance.
Luckily most parents recognize that a concentration of specialists provides better results than merely insisting there is nothing wrong with Junior.