Teachers where I live need, and have, the ability to apply violence to students. This is phrased as "physical restraint" and comes with extensive limitations and paperwork, the most important of which is that it is only allowed when protecting someone else.

What if one child wraps a skipping rope around another's neck and begins to choke them? Do you expect the adult staff to stand off to the side and do nothing?

Violence as punishment is different, of course.