Substitute any other actor for Jack Black and this movie becomes a direct-to-video blip, or doesn't get made at all. Black is Dewey Finn, a life-long rocker and true believer who gets tossed by his band and forced to get a job. Dewey snakes a teaching gig from his roomie, ending up at an exclusive elementary school with a stuffy principal (Cusack). There he finds a classroom full of precocious kids with musical talent and an entire spectrum of self-esteem problems. He molds them into a rock band with the intention of entering the Battle of the Bands. Some plot points are treated casually (sometimes to the point of ignoring them), but Black's wild-eyed, fully-committed performance easily carries the day, and he's ably supported by the kids, all of whom can actually play and sing, and by a savvy script that takes the music seriously.