The public educators I’ve spoken with are trained that any initiating any physical contact with a student even in self defense is strictly a liability and grounds for dismissal. The only permissible response to an assault from a student is for a teacher to use their elbows to cover their own abdomen (limiting damage to their internal organs) until the attack subsides.

While that instruction is to educators, I can’t imagine that school policy would allow student victims to respond any differently, because the parents of a bully with a broken nose could sue the school.