It's great that you want to advocate for your son. School is brutal. People will be more understanding if they are more aware. That's going to really make a difference for him later. I love my parents and they always support me but I've never discussed my stutter with them. I think we were all just assuming that it would go away (it didn't). I'm in college and i'm barely learning to advocate for myself and not letting people make assumptions about what I can and can't do. If I could give some advice, make sure your son knows that content is more important than fluency (and not to hit siblings haha).