I saw your post yesterday, then realized aculady and DeeDee had beaten me to the mark.
+1 everything they are saying. Your son is in the same place mine was in last year. Unstructured time at recess with no adult backup to help him negotiate conflicts was just too much for him. Things are slightly better this year, with closely supervised lunch in a small group setting with a facilitator, which he has been able to carry on to the playground for the following recess.
Whatever his label your son clearly needs some social skills training, and an adult to facilitate recess activities. Some schools in our areas have the SLP work on pragmatic language during recess with an "informal", open to all activity (legos, puzzles, games) to attract and mix special needs and NT kids. Should be in his IEP...