I agree with semperfiguy, try to get the assistant to calm him down. In my area, most small schools have one guy to coach, drive the bus, keep the books, tutor, and make sure the laundry gets done. It also depends on your relationship with the coach. You could walk over to the dugout and say, "Jim, can I talk to ya for a minute?" Once it is you and he, "Jim, I know you aren't happy with your kids but you can't keep going on in there like you are. I wouldn't allow it in a regular game and I am not going to allow it now." Most likely the assistant could get to him better, but it may come down to having to flex your muscle just a little.