I think the essence of being cool is having a sophisticated understanding of what is going on around you. High school geeks often find their environment tedious and can't be bothered to invest a lot of effort into figuring it out.
This is the thesis of PG's "Why nerds are unpopular", and having lived that life, I can assert he's right. Being polite, articulate, and compassionate doesn't hurt you in life -- and neither does intelligence -- but when it comes to "coolness" I think awareness of your surroundings is the most important key.