Before there was School of Rock, the 2003 movie in which Jack Black awakened a class of subdued elementary schoolkids with lessons in America's loudest subject, there was rock school. Students of the Paul Green School of Rock Music in Philadelphia have been worshiping at rock's altar -- and learning how to play the hell out of their instruments -- since 1998. Rock School, the fine new documentary about Green's phenomenon, takes a close look at the teacher and some of his students, ages 9-17. Through hilarious and charming interviews with the kids, extended chat sessions with Green, a few words from parents, and a healthy dose of performance footage, we get a sense of what sort of community Green has created, for better and worse. The central question is this: Is Paul Green a good teacher? On the one hand, he teaches the kids how to rock -- how to really, really rock. On the other, he's an asshole.