Spirited comedy pokes fun at rock world

“I serve society by rocking,” explains Dewey Finn (Jack Black).

That excuse doesn’t exactly sit well with Dewey’s roommate Ned (Mike White) or his friend’s harpy-like girlfriend Patty (Sarah Silverman). Dewey has been sponging off the pair for months, possibly years, while trying to make it big with his rock group.

Even more of a problem is that weeks before the impending battle of the bands competition and its $20,000 prize that serves as the Holy Grail of Dewey’s existence, his group decides to kick him out. Desperate for a way to earn his share of the rent, he impersonates Ned — who is a substitute teacher — in order to land a gig at an elite private school.

At first the job is one big recess for both teacher and class, but then he hears his fifth-graders making sweet music during their weekly classical lesson. With the big wheels turning in Dewey’s head, he formulates a plan to use the kids as his backup band to win the competition — once they’ve had a little high-intensity schooling in Rock 101, that is.

So begins “School of Rock,” a one-of-a-kind comedy that could have gone wrong in so many different ways that to sustain its harmonious tone is a truly impressive feat of filmmaking. The movie manages to appeal to both 30-somethings AND their children. It’s bust-a-gut funny without resorting to gross-out humor; it’s sentimental without being syrupy; and it’s charming without being manipulative.

Most importantly, it actually rocks.

As performed by the pudgy, wide-eyed Black, the central role in “School of Rock” is a masterful marriage of writing and casting. One can’t say enough about how much energy and conviction he infuses into this part. Black is simply astonishing as a true believer trying to champion a seemingly lost cause.

Actor/screenwriter Mike White, the creator of such daring indie oddballs as “Chuck & Buck” and “The Good Girl,” gives Black the perfect setup to exploit his comedic gifts. The writer also sidesteps many of the avenues that might turn this performance into a caricature.

Sure the concept of an outsider teaching life lessons to a ragtag group of students has been beaten to death by everything from the humdrum “Music of the Heart” to the annoying “Dead Poets Society.” But it all seems very fresh in the hands of Black, White and director Richard Linklater (“Waking Life”).

If there is one letdown to “School of Rock” it’s during the end showdown at the battle of the bands. While Dewey redeems himself by conquering a certain rock ritual that he failed at so miserably in the opening scene, the band doesn’t quite manifest the type of awe-inspiring performance that one expects after such a buildup.

It ain’t exactly the finale of “8 Mile.”

Part of the problem is the song they perform, which is written by New York rock revival act The Mooney Suzuki. The title track is a little too calculated in its attempt at conjuring the voice of a disgruntled 10-year-old.

But another concern is the group’s asymmetrical image, which could have been perfect if the members had stuck with their Angus Young-style school uniforms. Instead, the mismatched, spiked and teased attire looks perfectly cutting edge … if this were 1986. Now it’s more like a dated parody of the talent contest attire that the lead characters wore in “Revenge of the Nerds.”

Luckily, momentum is restored during a satisfying end credits roll in which Black and his students crank out a live-in-the-studio rendition of AC/DC’s “It’s a Long Way to the Top (If You Wanna Rock & Roll).” It’s enjoyable watching the kids caught up in the joviality of Black’s performance and with simply grooving to the tune that they are delivering with such feisty passion.

This extended jam is a perfect punctuation point to a film about how the only way to take rock seriously is to not take it too seriously.