The mental damage from being bullied, and having someone else fight your battle for you is worse than any memory of an ass kicking. A fat lip or bruises earned in a schoolyard scrap is nothing, less than nothing, in the course of your life. Being scared and being teased will shape your entire adulthood. I think boys need to learn how to cope with it, even if it means they lose a fight or two. In fact, fighting back doesn't very often go their way (too many people think the world works like Ralphie/Scott Farcas, and I got news for ya Scott wins more times than not). But, the resistance tells the bully this victim is not worth the effort or trouble, and sadly to some kids prone to this violence or resistance is all they respect. Walking away and having you step in, or a teacher, just fuels their anger and it also can prompt other kids to tease, harass or label the bullied and that's worse than whatever happened to begin with. Yes, your son's resistance will likely get him in trouble (with the school), but it will probably be better for his soul than any PC justice the school can deliver. Before you think I know not of what I speak, I have dealt with this with my daughter and she learned, as I said, that the harassment stops when she stands up for herself.