Stiles, now 19, is still wowing her elders–and winning plenty of admirers her own age. Save the Last Dance, starring Stiles as a sheltered ballerina who falls for a black hip-hop dancer, topped the box office during its first two weeks. And in State and Main she plays a ruthless teen who seduces a movie star (Alec Baldwin). Stiles's appeal? "She radiates intelligence," says Dance producer David Madden. Adds Baldwin: "All the smart girls out there want a girl they can call their own."
Coworkers describe her attitude as "mature" and "serious"–—but Stiles begs to differ. "I'm a lot goofier than it would seem onscreen," she insisted in a PEOPLE.com interview. As a freshman at Columbia University in New York City, though, she has taken on some added responsibility. "I've made a lot of good friends, and living in the dorm is really cool," says Stiles, who is considering majoring in English or Latin American history. But juggling classes with her Hollywood duties, she admits, is "really, really hard." While she filmed her current movies during a year off, after graduating from Manhattan's Professional Children's School in 1999, she now often has to race from classes to interviews and events like this month's Sundance Film Festival in Park City, Utah. Still, "in our family, we always thought of school as the most important thing you can do," says her mother, Judith, 49. "Julia really wanted to go."
Stiles's upbringing was decidedly unconventional. Judith, a ceramist, designs lamps, tiles and vases in the family's downtown Manhattan loft; father John, 54, oversees the pottery business but took a sabbatical this year to teach second grade in Harlem. They encourage Julia and siblings Jane, 10, and Johnny, 8, in academic, artistic and activist pursuits. At 6, says her mother, Julia "wrote a letter to Mayor Koch on how to solve the garbage problem in New York."
Stiles's theater work earned her an agent, and at 15 she landed a movie role as Harrison Ford's daughter in 1997's The Devil's Own. Meanwhile she and Ridge Theater director McGrath co-wrote a screenplay about a girl whose grandfather suffers from Alzheimer's that won admission to a prestigious Sundance workshop. "We got a lot of great feedback, but I haven't been able to go back to it," Stiles says. "I definitely want to continue writing."
Roles in the 1997 TV movie Before Women Had Wings and the '99 miniseries The '60s helped make her a hot Hollywood property–and leading lady of a spate of modernized Shakespeare movies, including '99's 10 Things I Hate About You (a retelling of The Taming of the Shrew), last year's hipster Hamlet and O, a prep-school version of Othello due this spring.
Stiles, who had a yearlong romance with 10 Things costar Joseph Gordon-Levitt, 19, lets off steam playing soccer in a league in The Bronx and has recently been dating her brother's soccer coach. The weekend footwork has paid off: A stand-in performed some of the ballet stunts in Dance, but "when [Stiles] saw the hip-hop double," says producer Madden, "she said, 'I am going to do it myself.'" She did–and the experience shows. "Look, it's Julia Stiles!" a fan shrieked at a Sundance party last week, spotting Stiles boogying to a Brand Nubian cut. "She really can dance!"
Serena Kappes, Sabrina McFarland, Elizabeth McNeil and Sue Miller in New York City, Michelle Caruso in Los Angeles and Elizabeth Leonard in Park City