I doubt the parents would teach them anything about behaving in class. They'd probably sue the school for not letting their child attend. When my daughter was in high school students would be suspended for their behavior and you would either see them walking around during the day or they saw it as a vacation.
Maybe the parents should have to go to a special class WITH the child and help the teacher teach their kid how to behave, sit still, listen, etc.
IMO a teachers job isn't to teach a child to sit. The parents have already failed miserably. What will actually happen....they'll slap some label on him and toss him in a self contained classroom with the rest of the animal like children and he can learn even more inappropriate behaviors.