He should go to a high school football game and ask them, that would be one of the best ways to get a good mix of religions and beliefs. I don't think you'll get too many teens here to help. You'll get more parents telling you what their kids think, your sone probably wants the info without the filter.
If he doesn't want to ask his friends, he could go to an out of town school where no one knows him, you never know he could make new friends too.
This post is not my usual it is actually something my youngest asked me to do since he is only 14. What he wants to do is get other teenagers thoughts on how they view religion, and why they think teens today may be drifting away from it? I will tell you we are catholic, and he would like to send the teens thoughts on religion to the new Bishop. The post is not about any one religion, but rather why religion has taken a back seat for the generations coming now. Thanks