Have you tried using a more positive approach? I learned as a mother of 2 (now 6yrs and 4yrs) that when I used the word "don't" or "no" along with the action verb...they focused on that action word. If I said "be quiet"...after telling/teaching them about quiet vs loud, they would be quiet or use their inside voices. Making it fun with a story or song is helpful (library should have something). Also, my kids like being rewarded. So, on issues that I want to work on with them, I'll reward them with something that they like. At first, I made a chart where they earned a sticker or stamp. After 5, they could get their prize (m&m's or smarties or skittles...only 5 pieces...helps with counting and/or colors, too...now, it's coins/money). I did a chart with 20 squares, after the chart was complete, we would go to the $1 Store! But it looks like you have a lot going on with the other kids. The parents would have to do something like this at home, too. Also, the 1-2-3 method works, especially in the beginning. If you give him a chance to listen, then he's more than likely to earn his reward and see that it's better to listen than to yell. I hope some of this helps! Good Luck!!