Always be sure to keep your personal style within the dress code set by your school. Your fashion statement won't be heard if you get called out of class right away about the questionable logo on your tee shirt, or the view of your boxer shorts peeking out of your pants. Working within the rules, you can still have style and enjoy being yourself. Choose clothes which appeal to you, first and foremost, as you're the cool one here, aren't you? Buying a shirt just because all the other cool guys wear that type of shirt doesn't speak so much to your own style as does a unique and interesting shirt that you personally enjoy wearing.
Enjoying your own unique taste and wearing clothes that you like can add to your cool factor. You didn't become cool by accident, so don't dress by accident either. Planning ahead, like laying out what you'd like to wear the night before, can allow to the time to carefully consider how you will be seen by other students. Choosing comfortable things you enjoy wearing will allow you to be yourself, and that's the best way to enjoy being a cool guy. Being cool from within, but the outward appearance is how others know about it, and you can tell them just how awesome you are by taking time to put some thought in what you will wear to school each day.