It is not a flawless film by any means, but few are. However it does address something that few movies about high school do; which is the dichotomy between students who live in the moment and think those years are the end all and be all, and those who see it as a finite time to get through for the longer (and hopefully better) future.
The main character's tragedy (among many) is not his ultimate fate but in that in seeking to get though the school years and not enjoying them (or what little there is to find happiness in) misses it, by being focused solely by getting out.
In contrast the other teenage characters (Rebel Wilson's being an exception) have blinders on; in terms of both acceptance of other people and of the existence of the larger world and that they will have to enter it and so forth.
Are there clichés? Yes, but high school students are much the same everywhere so that is an issue of reality and life and not the limitations of the screenwriter.
Are the scenes between Carson and the adults more compelling? Of course, but that is because adults by definition have more life experience (good and bad) to make them more intriguing.
Ultimately, the movie's flaws are minor compared to the whole. It is smart, dead on in observation (especially in regards to the parental and authority figures interaction with Carson and family dynamics), and the casting is brilliant, with one exception.
That would be Dylan McDermotte. Who, besides their mothers, can tell him apart from Dermut Mulroney?
