Her father teaches Shakespeare at New York University and her mother teaches sociolinguistics at Columbia, so it's no big surprise that certain things are expected of Lucy Deakins, 15. "I mean, you never get a C," Lucy says. "That's never done. My parents don't press it but, you know, they're into good grades." Lucy is into them too: She has an A-average and used to be crazy about marine biology. "I always wanted to major in it," she says, "but then I did a movie and marine biology sort of slipped in the standings. It just wasn't as exciting." The movie was The Boy Who Could Fly, now playing nationwide, and while the critics have found it less than exciting, they love Lucy. Variety said she had "amazing grace." Apparently performing has done more for Lucy than seducing her away from marine biology. "I was a painfully shy person in my pre-acting days," she says, by which she means before she got the play, the soap, the movie, the commercial and the Yoko Ono video.

All right, let's slow down a little here. It all began, the acting career, when Lucy and family went back to Greenwich Village from her parents' sabbatical in England four years ago. Lucy had found English kids kind of aloof, and being shy, "it was hard for me to talk to anybody except my family. Then I did a play and that was it—no more shy." The play was So What Are We Going To Do Now? in Circle Repertory's Young Playwright's Festival, and she was recommended by her teacher for the audition two days after she signed up for acting class at school. Lucy played a girl who decides to murder all the people who bother her, and she did it so well she got an agent and through him got the part of Lily Walsh in As the World Turns, which she played for 10 months. Then in April 1984 she won the lead in The Boy Who Could Fly, with top billing above Colleen Dewhurst, Bonnie Bedelia and Louise Fletcher. She liked them because "I learned so much and they were all willing to talk with me." She and co-star Jay Underwood, as the boy who believes he can fly, even did most of their own stunts, including a 50-foot free-fall in harness. "That was probably the worst," Lucy says.

Since she finished Boy, Lucy has done an American Greeting cards TV commercial ("a very short one") and an MTV video called Children Power, which was produced by Yoko and co-starred Sean Lennon. "I liked Yoko a lot," she says. So far there hasn't been any big conflict between acting and school, although Lucy admits, "there's a little jealousy at times" among schoolmates. At Manhattan's prestigious Stuyvesant High, however, most kids are more impressed by high marks than by stardom, and Lucy has both. Now she is doing a new play, The Hands of Its Enemy, by Mark Medoff, author of Children of a Lesser God. It opens at the Manhattan Theater Club this month, and for her role as the daughter of a deaf playwright, Lucy is learning sign language. What with Latin and physics, that's a heavy load, but Lucy has only one regret: She's never had time to go to a rock concert. "I was supposed to go hear Billy Joel," she explains, "but I had the PSATs the next day."