Have you tried looking for a teen monologue in an anthology? Lots of publishers sell monologue collections; the only problem is that most of the monologues are for actors in their mid-twenties and above.
The monologue books that cater to teens often present "problem monologues," dramatic speeches that focus on serious issues such as suicide, drug addiction, and teen-pregnancy. Sure, these are all compelling subjects. But I've noticed that many of these monologues are woefully heavy-handed. They try too hard to capture teenage angst, or try to hit the audience over-the-head with a "life lesson."
That's why I'm always on the look-out for good monologues for teen performers. Any scene or speech that is fresh, original, and doesn't talk down to its reader/audience is a rare treasure. When I do find that sort of monologue, assuming it's public domain or written by a contributing author, the speech is placed into our growing library of acting monologues.
So, if you know of any online plays, favorite scenes, or original monologues of your own which you'd like to share, leave a comment, or launch a discussion in the Plays/ Drama forum.