Personally if he was screaming while waiting his turn he would be put in timeout (the 4 minutes of timeout time doesn't begin until he begins to sit quietly and not scream). That is not proper behaviour. Then when he gets out of timeout he is last at taking his turn or misses whatever is going on altogether. He sounds very similar to a boy I had last year. I was so happy when he was gone!! That was a very long year that I had him. He too was an only child who catered to every whim and was a little s&*t when mom or dad picked up. IMO children like this need discipline so they realize it is not acceptable behaviour in your home.