what matters most to him? sometimes time outs don't work for some. I had 1 boy who hated being last at things. If he was acting up then I made him go last for everything. Also when you put him in time out then do something fun with the others that he can't participate in - like coloring or playdough. I have given kids rice cakes for afternoon snack while others get cookies etc. That kind of things. I would still do the timeouts but include something else.