Your child is being taunted and called names, you call the school. You child is being assaulted, you take them out. No ifs, ands or buts. Take your child out of the place where they are being hit.
This is not "preparation for life". If, as an adult, you are assaulted you call the police. If a co-worker shoves you into the wall and hits you they are fired.
That is the way the adult world works.