When my son was in the 7th grade, at a Catholic school, his class went on a field trip a couple of weeks before the end of the school year. The bus had two teachers on board. One of the boys walked up the aisle slapping other kids in the head. My son was one of them. He didn't react. Two girls sitting behind him told the teacher. The teacher told the principal, Sister Jeri, who called me. The kid got 1 hour detention each day.
I told Sister Jeri that my son had been trained in self defense, and I was going to change my instructions to him about what to do in these situations. I had previously told him to only fight back if he really needed to in order to keep from being hurt. I told Sister Jeri the new instructions would be that if is struck first, to do whatever he needs to do to make sure he's not struck again. I added that someone would end up being hurt, and that I would expect no more punishment than detention, because that's the standard.
Sister Jeri said she thought the other kid was just playing. I asked her if she had ever been struck in the head, or otherwise struck in anger. She said no. I told her that boys play by hitting a shoulder, but never the head. She didn't understand that.
The bully didn't return to school the next year. Seems a couple of other parents had discussions with Sister Jeri as well, including a dad who happened to be a Bird Colonel in the Army. Sometimes educators need a real life example to understand the world isn't necessarily kumbaya.