That's just the life that School of Rock's Dewey Finn leads, and just barely. Dewey, played by Black, is still chasing Barry's dream: He's the stage-diving, solo-taking guitarist in a hair-metal band that thinks Dewey an embarrassment, a no-talent who'll keep the band from winning a local battle of the bands -- a real punch in Dewey's ample gut, considering the band resembles a third-rate Poison tribute act. Disgraced, he takes to sleeping all day on the couch of nebbishy Ned (Mike White, who also wrote the screenplay) and Ned's girlfriend, Patty (Sarah Silverman), who demand he get up, get a job, or get moving.
Dewey, assuming Ned's identity, ends up teaching at a hoity-toity private school. His idea of learnin' is telling the kids they're doomed to be failures. Then he overhears them jamming in music class and figures he can prod the prodigies into joining his group, which involves deceiving the principal and taking the kids out of school, inexplicably without consequence to Dewey.
Linklater seems delighted to romp in the mainstream. The filmmaker hasn't made something so enjoyable since Dazed and Confused, a bong hit of a movie. School of Rock is light and meaningless but never worthless. It merely aspires to be a good time, and it's just that and nothing more, a grin-worthy buzz that wears off in the parking lot.
Of course, the movie would be less than nothing without Black, finally allowed to charge ahead without a director acting like his movie set's a china shop. School of Rock would be saccharine without him. Black plays himself, meeting the expectations of those enamored of his convulsive outbursts and eyebrow spasms. His is a curriculum of metal moves and guitar-hero histrionics taught to kids who were hired because they could actually play. Dewey's the sub you pray for but are scared of when he actually shows up, with his eyes wild and mouth screwed into an ex-con's grin. Without Black, School of Rock wouldn't pass.