well I'd assess whether he really wants this and whether or not this is a peer pressure thing. What it boils down to is you're the parent and he's the child and his body is your responsibility until he is 18, after that whatever he does to it is his business. I'd sit down with him and have a talk with him and ask him to make sure this is what he really wants, because the results are likely permanent and irreverisible. Did he want the same things at 5 and 6? Therefore, will he regret the this by age 19 and 20? Remember, you're his parent, not his friend, and though he might be upset if you say no, he might thank you when he is older.