Most people will tell you the right thing to do is to not trade-up. However, I do not completely agree. While going back on your (son's) word would cast him in a bad light with the spurned program, At the end of the day, who cares? The new school is the one your son has to please. If it's his top choice and would be happier there, he should take it. I believe, that at a lot of schools, if your soon took a while to decide and in the interim the school found a stud and had no $$ left, they would give away your son's spot in a heartbeat and say "We didn't hear from you so we figured your son was not interested. We had to fill our class." Your son should do what is best for him. Just my inexperienced opinion.