If Eighties teen films were underpinned by anything, it was winning, and winning in style: whether it was being co-opted by the army to build super-lasers (Real Genius), piloting a space shuttle back to earth (Space Camp) or avoiding having sex with your mother and driving a cool car (Back to the Future). Richard Linklater's latest film, the marvellously funny School of Rock, pays homage to these feel-good films but expertly reinvents them for the grown-up slacker generation of 2004. If not quite touching generation-defining status, it certainly feels like a very prescient piece of work.

Linklater is of course no stranger to the weighty "definer of generations" tag. While he dismisses it as "flattering but painful", Slacker, his 1990 debut, eloquently brought Generation X to the big screen, with its loose portrayal of a day in the lives of twentysomething dropouts in Austin, Texas. He followed it with huge cult hit Dazed and Confused, an arguably near faultless journey through a hot summer day and night on the last day of high school in 1976. Since then there have been a couple of blips (The Newton Boys and SubUrbia) but enough highs (Before Sunrise and Waking Life) to ensure that his indie-cinema pin-up status has flourished.

School of Rock is most definitely a high. It follows the fortunes of slacker Dewey Finn (Jack Black), a die-hard rocker who stopped listening to new music in 1986. "He's a bum," says Linklater. "He could have stepped out of any of my other movies. If you want to go back to Slacker, he's seen by society as an unproductive citizen who has nothing to offer to anybody." After being thrown out of his band for indulging in lengthy solos, Dewey needs to pay the rent, so impersonates his flat-mate and gets a job as a supply teacher at a prep school run by the stone-faced Rosalie Mullins (Joan Cusack). Initially, doing any teaching is too much of a chore, but discovering how little his 10-year-old pupils know about the ways of Led Zeppelin, Dewey decides the class project will be to form a high-voltage rock group and enter the local battle of the bands. The kids unite behind him, the headteacher softens to his charm and, well, you can probably guess the rest. As familiar as the formula may sound, School of Rock excels both in its mirthful deconstruction of rock posturing, and in the way it redefines the notion of success in the mirror image of the slacker generation.

"It was interesting to play with the idea that a guy could find his niche in a crumby world that has all the wrong emphasis," says Linklater. "Dewey is under attack, his ideal world is not really working out. In a comic way I was hoping to show that everybody has something to offer and there's still a place where your passion can be translated. It's not like these people are lazy or not motivated, they are just passionate in a narrow range."

Dewey's niche, it turns out, is to set up an after-school music club in his living room, contrary to our expectations that he'll either get a load of cash (The Goonies) or be catapulted into the life of a music mogul with a fetish for aviator sunglasses and fine restaurants (Ferris Bueller's Day Off). Nothing really changes in Dewey's life but he becomes immensely happy. And so are we: we don't feel cheated that he doesn't go on and become a rock star. It's a vision of success born out of slackerdom. Dewey is the embodiment of Slacker's famous contention that "withdrawing in disgust is not the same as apathy" and he takes the creed to mainstream acceptance: you're in a band and you teach kids how to rock? Fantastic. What a great way to spend your time. If you were looking to define "the now", where a generation resists any definition of itself, this is perhaps a good point of entry. Whether you think this reflects a real undercurrent of "the now" is of course entirely arguable. But Linklater's films tend to become marked as such.

"It's flattering to have something you did be seen to be tying in with anything in the world," he says, recalling the hype that seized hold of Slacker. "But then other people start tacking on so much meaning and it becomes that 'definitive' thing."

Unpicking what constitutes a generation-defining film is a tricky business. What counts? The Fifties teen deviance of Rebel Without a Cause? The Sixties pop cultural flickers of Blow Up? The perfectly realised Eighties high school archetypes of The Breakfast Club? All could be considered to have captured an underlying essence of their time.

"It's all about familiarity," reckons Linklater. "It's successful in my mind when a film breaks down from being an entertainment commodity and mirrors something in your own life. People reach into films: that's what works with Slacker, I suppose - it validated a certain lifestyle or a time in people's lives and that's how they found their way into it."

Not that he's entirely happy with us squinting too closely. His advice to would-be generation-definers? "If there was a way to do it, my first rule would be to try not to do it," he laughs. "I don't really think that way. My films are just one little bitty story from one little bitty place and one little bitty time, and you can take it or leave it."

'School of Rock' (PG) is released on 6 Feb