My in-laws picked up the kids yesterday from school for a spend the night visit, so Lawton and I were just now able to speak to Will about what happened Friday. Here is where things get interesting. I was all prepared to give my usual lecture about not fighting, getting a adult to help you, walking away, etc., when he said, "Well, he (the other child) touched my privates."
You could have heard the mental brakes squealing at that point. Lawton and I looked at each other and could tell we were both thinking the same thing, which was GOOD JOB. Now, I realize that him finding his teacher still should have been his first move, because she wasn't that far away. But I also firmly believe that kids should be taught that while you shouldn't go looking for a fight, you have the right to defend yourself if need be and you sure as hell have the right to, shall we say, deter, someone who gets all up in your junk.
The problem is helping him understand the difference. He was thoroughly confused when we told him that while we wished he had located his teacher first, we totally understood him reacting like that to someone touching him inappropriately. Cutting in line for the water fountain isn't grounds for punching someone but neither do you have to let someone rough you up and not defend yourself.
This is so intangible a lesson and is so hard to communicate because what I WANT to say and what I SHOULD say are not always the same thing. It's kind of the same feeling you get when they are little and get bitten in preschool. I've never wanted to slap the crap out of a two year old until they drew blood on my daughter's arm. I didn't obviously - but that is one of those things as a parent that is so hard to deal with mentally. What we want to do versus what we should do when someone hurts our young ones.
As far as Will goes, we will always encourage him to walk away, as we would given the opportunity. But you know what? Someone touches my stuff without permission and I'll probably punch them in the eye too.

