Lets all be realistic and support the original poster, she can't kick her own son out of daycare. She is looking for solutions for her program.
The best advice I have is watching the boys play as much as you can in order to see the aggression pattern. If hes biting out of frustration due to toys being taken away than correct that behaviour right away etc...
Understanding what is the motivating factor is parmount for success.
Also the best part of our daycare is running our programs based on our own value systems. I am sooooooo greatful for having found parents who are on the same page as me.
My style is lets prepare these kids for the real world, not every encounter in our lives are going to be pleasent, how we learn to problem solve and deal we these situations is the key to success.