The 'Rushmore' alum heads back to school in 'Slackers'.

Jason Schwartzman is no max fischer. For starters, there’s his uniform: sweatshirt, old sneakers, well-worn jeans. Then there’s his hair, which hangs so far over his forehead it all but obscures the actor’s famously bushy eyebrows. And certainly, Max Fischer — the bratty prodigy Schwartzman played in Wes Anderson’s Rushmore — would never be sitting in a Manhattan deli, chugging heartily from a gallon of water, and dishing about Mamie Van Doren’s breasts.

”She had this body makeup on,” Schwartzman says, describing a scene in his new comedy Slackers, which finds him getting intimate with the 69-year-old former sex kitten. ”And then later on, at lunch, I had this…thick film on my teeth. I couldn’t taste any food.” He pauses, guilt passing across his face. ”Should we put this in there? Do you think she’ll get mad?”

If Ms. Van Doren were to take issue with his description of their brief encounter, it’s likely Schwartzman could disarm her with charm. At 21, the easygoing actor has a knack for making even the most seemingly ironic statements drip with sincerity. And if Schwartzman and his Rushmore character have anything in common, it’s the need to exist in a state of constant creativity. Which is not surprising, considering his pedigree: His mom is Rocky actress Talia Shire; his dad, who died when Schwartzman was 14, was producer Jack Schwartzman (Never Say Never Again); and the man he refers to as ”Uncle Francis” just happens to be the director of The Godfather.

It was Francis Coppola who in 1995 hosted a retreat where family members staged shows. The 15-year-old Schwartzman’s contribution centered on a group of men at a bar on New Year’s Eve, all reminiscing about the same dead woman. ”I really went for it,” Schwartzman says. ”I’m not saying it was good. I’m saying…is ostentatious the word? It was ostentatious.”

Despite this early theatrical success, Schwartzman was more interested in practicing drums than drama. His L.A.-based power-pop band Phantom Planet signed a record deal when Schwartzman was 14 (their second album, The Guest, will be released Feb. 26). He didn’t contemplate acting until his cousin, Virgin Suicides director Sofia Coppola, introduced the then-17-year-old Schwartzman to a Rushmore casting agent. But for the most part, that’s where the family connections ended. ”They’re all wonderful people you could call on for advice,” he says. ”But I decided to make it more between me and Wes and Bill [Murray, his costar].” Critical kudos, a cross-country bus tour with Anderson, and cult stardom followed. Upon returning home, Schwartzman took a break from acting and attended classes at UCLA.

Then came Slackers, which finds the actor graduating from high school misfit to college misfit (it was shot for Destination Films in 2000, but was held up after the indie closed shop last year). Fashion photographer-turned-director Dewey Nicks first met Schwartzman through Sofia when the actor was 13. ”Even at that point, he was definitely the star of the family evenings,” Nicks says. ”We’d all go hang out in the garage and watch him play drums.” Fittingly, Schwartzman performs two songs in the film, in which he plays ”Cool Ethan,” a geek who stalks comely coed James King.