I went totally nonviolent when I was 8 or 9 in 3rd grade and stuck with it until I was 15 in Junior High School. Would not fight back, would not defend myself physically. I’d get furious, defend myself verbally, and would indeed go and tell the authority figures if I were being assaulted or harassed.
Here’s my results:
• Anger and fear twist your stomach all to pieces and leave you shaking, and people can tell, and they find it funny and taunt you & pick on you more because they can tell that they are getting to you
• Other folks’ mileage may differ, but I started out with the impression that the adultworld was a world not run by coercion and intimidation but instead was one in which the righteous law-abiding civilized citizenry were in charge, one where principles came before favoritism or opportunism, one where with rare exceptions the people in authority did not use their authority to favor themselves or their friends or their personal causes but instead weilded their authority with great fairness and even-handedness. By the time it was over, I was pretty much of the opinion that the people in charge were in charge for no particular reason other than the fact that they’d won the power struggles, and that as long as there existed people who liked power over other people it would be those people, to a disproportionate extent, who would rise to positions of authority as long as such positions existed. And so, ultimately, when I was running to “tell the teacher”, I was most often turning to one bully for protection against another.
• I was not especially admired by the adults for being “civilized”, for being self-controlled and self-disciplined. In fact, male adults were often contemptuous of me, hostile, said I was “sneaky” and was somehow cleverly setting up and doing in those fine young men whom I was accusing of harassing me. As I got older, female adults were less and less sympathetic and occasionally hostile as well.
• When you stay out of fights from the age of 9 to the age of 15, you’re effectively unable to fight. What you once knew you’ve forgotten, and a nearly full-sized person who tries to fight as they did when they were 9 isn’t going to be formidable or effective. In particular, little kids don’t put their weight behind their blows because they don’t have much weight, and they do their damage by flailing.
• Lots of anger and fear that isn’t given an effective outlet tends to ferment and turn very dark. I can totally imagine my 5th grade self up in a clock tower with an automatic rifle. I had significant and powerful and perpetual hate for a great many of my classmates, mostly boys. I did not want them to accept me, I did not want them to like me. I wanted them to leave me the hell alone, and really I just wanted them to not be. Such people should not exist, their very existence was an effrontery.
My advice would be to discuss violence and authority and the relevant moral and philosophical issues with the kid. These matters are no more beyond the mental capabilities of a grade-school kid than mixed fractions. Instead of telling the kid to DO THIS when THAT happens, get into conversations about the outcome of doing ANY of the possible things one could do in response to violence. Everything has consequences. DON’T make the kid promises that “if you do XXX, everything will work out all right and get properly and fairly straightened out in the end”.