He is a teenager. Obviosuly, you don't want him going to strip clubs or bars, but beyond that, I'm afraid to say you don't have a whole lot of control over where he goes. Sure, you could coop him up in the house, or set strict rules, but is he really going to be a better Christian by you doing that? No, he'll just be more eagar to sin after his 3 remaining childhood years are up. Talk to him, explain to him what your feelings are, but beyond that, it's his decision. He's 15; he knows right from wrong by now.