I'm a teacher, and it makes me so sad how schools have responded to a few crazy parents or groups who want to censor or see monsters in totally normal behaviors. I wish your family were closer to my school, because we understand "normal" boy behavior.
If only for your own peace of mind, read these two books:
Killing Monsters: Why Children Need Fantasy, Super Heroes, and Make-Believe Violence by Gerard Jones;
Raising Cain: Protecting the Emotional Life of Boys by Dan Kindlon.
You could also read Ralph Fletcher's book _Boy Writers_ which addresses a lot of the "issues" schools have with boys within the context of good writing practice. It's a great read.
Honestly, I think talking to your son, being a safe place to ask questions and say what he's thinking is the best thing. In terms of what's happening at school, I think a more proactive approach is to either ask the boys to come up with alternative activities to fighting/playfighting they might enjoy (and keep that list laminated and on the playground even) or to actually engage them in a game or activity as recess monitors.
By the way, my very normal, very well-adjusted, very bright 8th grade boys GLORY in beating the snot out of each other and rolling around like puppies. Their favorite "game" right now is slapping each other in the face or in the stomach when someone least expects it, then running away. Kicking/punching each other in the groin is their second most favorite activity. We don't allow it on campus, but it's not a major issue because we talk to them about appropriate place and time. I tell them to make a playdate and clear it with their parents, and then I have no issue if they beat the snot out of each other.
This is the "appropriate" way in our society for men/boys to touch and show affection. Have you seen a group of men hanging out together? It's the same game, just tweaked a bit.
SD
Me: 40 H: 43 H had EA from 2/06-9/06 Bomb 5/06 Piecing since 9/2006 3/2008: Boundary setting 7/2009: Boundary crossing~dropped my own bomb. 8/2010: Marriage finally on track!