Its a status thing. They don't want to date someone who will affect their social status at school so they date just the popular ones. Its stupid, I went through that. Here I was thinking I was ugly throughout high school, when really I was not haha. I actually have been getting a lot of emails, facebook messages, etc... from guys who went to my high school who thought I was hot. They didn't date me because I wasn't 'cool' enough.
Well sorry guys, but I as pretty awesome back then, and I am even more awesome now too and that boat has sailed :P
But really, guys will get over this once you hit your early 20s. And then they will be begging to have you go out with them ;)