I think yaoifun has got it right. Surveys of adult penises haven't shown any increase, and I doubt teens have changed drastically physically just recently. But what has changed is that guys at school no longer are required to shower nude together, and no longer get changed for swimming etc as openly. Therefore they lose contact with a real average, and only see the guys who show it off or at least don't hide it, who are mostly the hung guys. I think there is a more competitive spirit around now too, which makes the smaller guys ashamed and they take extra care to hide it.

So I think, Briandude, if the guy next to you had been small, he probably wouldn't have let you see. He might well have avoided the urinals altogether. And huge, does everyone in your school shower, or do some avoid it?