Um, I am anti-social and a theater kid, which is far cry from a normal high-school kid, but we tend to hang out at Dairy Queen after opening night? Most theater kids are into Jimmy John's though. I know a lot of people do just hang out at each other's houses, school sporting events for sure, and extracurricular activities.
I don't think many normal teens actually have that much free time because of all the things they do.