well then why not put the bad apples in the gym room or the office so the 6542529 other kids who do behave themselves enjoy 20 min of fresh air during recess
because the parents then sue the schools saying their child is being treated unfairly, it's a violation of his civil rights, blah blah blah.
it's a small amount of parents who hold just as much blame as the government for the state of todays schools.