There is the Young Adults section, which is aimed at college age. I think it's just that the majority of teen/college age are in the chat rooms, not the forums.
And threads are started by users, so anyone can start a thread on it. Which would be most fitting in the YA section, but as i said, it's already aimed at that age range to begin with. But if you really wanted a thread on it, then go for it. Best way to do things here is start what you want, rather than wait for someone else.