One strategy I have put in place is a token economy to use during playtime to encourage appropriate play. Tokens are given for appropriate play throughout playtime to work towards a reward at the end of play if he has 5 coins on his chart. The teacher on duty wears the lanyard around their neck and provides continuous positive reinforcement for the desired behavior.
There are many different tokens you can use, I have used the same coin system that Tamaki Primary have used for their school wide points system.
http://www.educateautism.com/token-economy.html