Perhaps you should call on a regular basis and make your case over and over again. Using a respectful tone of voice is important. You do not want to become confrontational, but persistently asking for your son to be allowed to go back out for recess might pay off. You could point out that your son needs to get exercise and sunshine. You could say that you are concerned that he will begin to see adults as unfair. You could tell him that you agree that he can do what he wants with his school, but you would expect that what he wants is what is best for the children. Best of luck.