Jack Black made his way into the hotel conference room for his Dallas interview looking a trifle ragged. “Last night I chowed down on some amazing Chicago barbecue,” he explained. “Had horrible heartburn—I don’t know if it was heartburn or just indigestion. Horrible pain, right here. Couldn’t sleep very well. Roll-Aids, four Roll-Aids. Out like a light. I had four hours of sleep. I woke up—it was difficult, I heard the wake-up call. I easily could have slept another five hours. But for the good of the film, I dragged ass out of bed to meet you fine people to talk about my crowning achievement.” The last words, of course, were delivered in his patented sarcastic drone.

Though he’s played a surprisingly wide variety of supporting parts in films since his debut in “Bob Roberts” back in 1992, Black has always had a special affinity for roles involving rock. He’s probably best known for his turn as a fanatic music store employee and would-be performer in “High Fidelity,” and his stint as lead singer in the comedy group Tenacious D has made him an MTV favorite. Now Black takes on his first solo lead in “The School of Rock.” He plays Dewey Finn, an obsessed guitarist who cons a posh elementary school into taking him on as a substitute teacher and trains his fourth-grade students to form a band.

“There was some concern going into it,” Black admitted. “They say you’re never supposed to work with kids or animals. I, however, was not afraid, as some of the cowardly old men in the history of Hollywood have been afraid. They’re afraid because the kids are so adorable and the animals are so cute that they will steal focus from the star. I was up to the challenge. I said, I will do battle with these kids. I will battle their cuteness with sheer intensity—not wit, that’s not my strong suit, wit has never been my bread and butter. Intensity, passion rocks!” Anyway, Black added, he felt at home with the children. “I’m kind of a kid,” he said. “My sense of humor, it’s no secret, is a little immature. I’m stuck in adolescence in many ways. And so if you remove all the cuss words, actually I’m perfect for a kids’ movie, as it turns out.”

Not that “School of Rock” is a typical children’s picture. It was written by Black’s old pal (and one-time neighbor) Mike White (“Chuck and Buck,” “The Good Girl”). The director is Austin’s edgy Richard Linklater (“Slacker,” “Dazed and Confused”). “[Richard] was the only one that Mike and I wanted to work with, because he had a lot of integrity, and with a kids’ movie, you know—even with a great script like Mike had written–there’s always the danger that it’s going to slide into a cheesy, corn river that goes into the hot and corny ocean. We knew that he wouldn’t let that happen. This is a kids’ movie, but the problem is, most kids’ movies are lame. And we were on a mission to make a kick-ass kids’ movie, in the tradition of “Bad News Bears,” “Willy Wonka,” “Sixteen Candles”—and that’s it, basically. No, there are some other good ones, but I can’t remember them. And by God, I think we’ve done it.”

Much of the picture’s fizz comes from Black’s manic performance. “It’s tiring. It’s not physically difficult to do it, but it’s just psychically fatiguing to, like, be high-energy crazy a lot. So when we’re not filming I just try to be mellow and hang out and chill and zone out. I played some video games in my trailer in between takes…I like video games, it’s no secret…not a good one, but once I start a game, I really feel like I have to finish it—I have a little obsessive-compulsive disorder. I had to conquer it, and I did conquer it, thankfully. I have this weird superstitious thing like if I don’t conquer the [game] that I’m doing while I’m doing the movie, then the movie will be bad. That’s bogus, by the way.”

When asked what message “School of Rock” was intended to convey, Black was nonplussed. “I don’t think about messages when I’m making a [movie],” he said. “I think about what makes it funny and entertaining. I’m a crowd-pleaser by nature, not so much about making [the audience] think about stuff, like a soul-search. But if it does that, that’s cool. I think [“School of Rock”] says something about having the courage, you know—God, it just feels so cheesy as soon as I start to talk about a message—to follow your heart, man, to follow your heart and your dreams!” And then amid the laughter, Black added: “It doesn’t sound like a movie I want to see when I start talking like that! Mostly I just want people to laugh and have a good time and want to see it again.”

One member of the press interjected, “It’s a nice flick,” to which Black replied, “Thank you. Nice flick? I don’t know,” with just a touch of feigned discomfort. “It’s very entertaining,” the interviewer added. “Warmer,” Black encouraged. “We loved it!” another said. “Good,” Black responded with a smile. “We’ll leave it at that.”