Happy Birthday Matt is self explanatory.
I believe that one of the reasons that adults are better adjusted than teenagers is that teenagers are forced by the state into situations in which they are forced to interact with every other type of person. As we get older we self select into more and more selective groups. During high school, we are forced to attend classes with every other type of person. We have to do everything from grade their papers to shower with them. We are inherently uncomfortable with these people because they are not like us. Yes, in high school we separate into cliques, but those cliques are not closed off. They are forced to interact with other cliques. As adults, our interaction with people that are not in our self selected group are very limited and brief. I think that high school would be more effective and less traumatic if the students were allowed to choose in middle school: where they attended high school, what they would study, and who they would study with.