As for the Topic of the Day...
I guess I'll mention "Ordinary People" too. It's one of my favorite movies. However, I see it more as a "troubled family" movie, rather than a "troubled teen" movie. I first saw it back in high school in Social Studies class, and it was a fascinating movie to discuss with other high-schoolers/teens.
"The Breakfast Club" - One of the few movies I've seen more than once in a movie theatre. Of course, that may have had more to do with Emilio Estevez playing a gymnast than anything else.

"Ferris Bueller's Day Off" - I actually did not see this movie until a few years after it was released. I had just heard so much about "Bueller! Bueller!" that I was put off by all the hype. However, after catching it on HBO one day... -Just what is Alan Ruck up to nowadays anyway? *And I remember seeing
Biloxi Blues on Broadway with both Mssrs. Broderick and Ruck.
"Stand By Me" - Well, maybe troubled "pre-teens".