As much as I am reading some comments and agree with them, I want to add my own “2 cents”. I am someone from a frum background, who in his later years is having trouble remaining frum.
I believe if one tends to “explore” other options at a young age, he will be more likely to hang out with this chevra for a year or two, and eventually come back. I’ve seen it happen on many occasions, and they are doing quite well in the yeshiva world.
I, on the other hand, is struggling later in my 30’s as if I would have done so in my earlier years – perhaps by now, I would have been “choizer” already.
What I’m trying to say is, he’s a teenager. They go through fazes in life. They like to try out things. Being in the Frum world, people think that if they hang out with a bum crowd – automatically, they are going OFF THE DERECH. Its not so, they are just in a teenage faze. If we would look around at our goyishe partners in our lives, we would see it happens to their children too- just on a different, perhaps higher scale.
Drugs abuse, alcohol, parties… etc. When we see our kids (who are in FRUM YESHIVISHE high schools) we don’t think to expect our kids to do something like that. And even if something does happen- on a much lower scale, we tend to go berserk and chas v’shalom, the kid should even be thinking about doing those things. I say- the younger one experiences this, the quicker he will get “back on track”… if you push him to do something he doesn’t want to do- and tries to please you all the time, then there may be more consequences later on his life, when it may be too “late”.
Let him try out his latest fad, hang out with this chevra who you claim is “going off the derech”… and he will come to his senses quicker than you think. And just relax, accept him… help him. Perhaps tell him, there are some groups of guys hanging out in such and such a place (NCSY, etc) and let him experience different folks that way in a much better settings. NCSY is very good at what they do, and they provide a atmosphere which allows the teen to feel he is not alone, and that there are others like him in this situation, yet a steadfast jewish. And it also comes up with well-trained yeshivish chevra who can keep him on track.