In all honesty, it differs with each kid.
I got jumped at a party when some kid had his friends turn out the lights. He tackled me from behind and hit me in the face. I kneed him in the balls, got him off me, the lights came on and he was standing there with hands up ready to go. I stared at him and his 3 buddies around me and all the people in the basement, and asked, "What the hell was that for?" and walked away. I got a call from a girl I had a thing for the next night and she was all over me saying how big I was for walking away from it. The guy who hit me was ostracized by all the girls for a long time after that. He didn't frick with me again. Embarrassment goes a long way, I guess.
My brother got jacked in the face as he was getting off the bus. He went full rage mode and had to have his buddies pull him off the kid when a neighbor said she had called the police. He couldn't ride the bus anymore, but nobody fricked with him again.
Each situation warrants different responses. Typically, it involves the parents talking with the bully's parents, but you never know how that will play out. He'll figure it out.
This post was edited on 12/5 at 9:52 am