When I was about 6 years old, I got into an argument with a neighbouring child who hit me. I walked back over the road crying to my Dad who was working on his car on the drive. He showed me no sympathy and immediately sent me back over the road to hit the kid back. I did (I was more scared of my Dad than the other kid) and the other kid then went off crying.

Not sure I'd do the same with my son (if I had one, I only have a daughter).