Does your son like his current team? Good coaches? Having fun? Does your son like playing the game? Is the team competitive relative to your son's skill level? If so, then why leave? Re-evaluate those questions year-to-year. If your son is good enough to make a top tier high school team when he gets to that age, he will make it. If you son is already in one of those programs that has top level high school teams and a new kid shows up who is better, that new kid will take your son's spot, regardless of how long your kid has been there.