Who cares, really?
As for clothing cliques... You serious? Whos ever heard of a clique that all they do is judge what people are wearing, I have never seen nor heard of one.
You're obviously a nerd. It doesn't matter if you go to school with a bunch of wealthy elitist brats or if you go to school in the Brooklyn ghetto, people are going to judge you buy your clothes. If you don't think so then you need to open your eyes and take a look around. Preppy kids hang out with preppy kids. Gangstas hang out with gangstas. It's all determined by your dress. If you're thinking "no, its not because of their dress, they hang out because they have similar interest" then think about what would happen if a preppy kid who likes rap music tried to join their group. Obviously things wouldnt work out.
Also, wait until you go to college and try to get into a fraternity. Generally guys are required to maintain a certain style of dress for certain activities. Obviously you aren't expected to wear polo's to the gym, but you get the point. And for girls it's even worse. MANY sororities have rules regarding what styles and brands girls are and are not allowed to wear.

