Interesting question. I know that in some schools, there are administrators and some teachers trained on how to restrain students who become violent. There is a specific “hold” they can employ if needed. But this is only used if the student is assaulting someone. A push isn’t necessarily aggravated assault but then it depends on the strength of the push. But I don’t think adults should “push” students back if they are pushed. It just doesn’t do anything but escalate the situation.