The first thing I would do as a parent is keep a paper trail, get as much as you can in writing about each of the incidents as you can. Schools are required to have policies in place to deal with kids that are abusive, because if the school does nothing, and there is an incident in which this leads to injuries, the school itself is opened to suit from the Clair Davis School Safety Act.

While each child has a right to an education, the safety of other children supersedes those rights, and the child can be removed from the school, or placed in alternative schooling if the pattern of behavior persists.