It's the individualization. Someone could be seething inside, a walking time bomb. It's knowing their history, knowing the previous ways they manage. I'm trying to say it's an art. I guess there's an understanding over the years that strict compliance is not really the way to effect change in kids.
Much more effort is put into trying to understand and remove the triggers to acting out or violence.
Sometimes you could teach them writing in a journal, doing exercises like push-ups. You can't stop an emotion if you don't provide an alternative. A person who goes to attack you and swings at you is probably experiencing intense anxiety. Unless you offer them something to do with that, you're fighting a losing battle. You don't want to meet force with force.