Kellie Martin's series stardom -- We talk with the ''Life Goes On'' actress about the joys and pitfalls of being in the spotlight

Even for a star, some adolescent rites of passage can be as difficult as anything in a John Hughes movie. Take Kellie Martin and her First Big Kiss. This fall, 15-year-old Martin began her second season as brainy, witty Becca Thacher on ABC’s Life Goes On, and the producers of the family drama had a welcome-back-from-vacation present for her: They arranged for Becca to fall for a tall, teenage Hawaiian surfer and pucker up right in front of 14 million viewers. Of course, it was only pretend, but a kiss is still a kiss, and to make it more unnerving, the actor playing the hearththob was 24 years old.

”I was shocked,” recalls Martin, giggling and blushing, in a Warner Bros. commissary after a morning of filming. ”They always hire older actors to play younger, but I met this guy and went, ‘HELLO! You are a man!’ He looked like he could be my father. But he was very gorgeous indeed. Very, very gorgeous. I had a big crush.”

The prospect of a public embrace may have flustered Martin, but she regained her composure and did the scene. And her fling with the guy proved brief. At the end of the episode, which aired earlier this season, ”Becca dumped the surfer,” Martin says. ”Her love life is a lot more interesting than mine.”

Martin’s beleaguered Becca has become the unofficial star of Life Goes On, which airs Sundays at 7 p.m. opposite 60 Minutes and has grown increasingly strong in the Nielsens. Last year, ABC’s promotion centered on Chris Burke, who plays Becca’s 19-year-old brother, Corky, and, like his character, has Down’s syndrome. Early episodes focused on Corky’s traumatic adjustment to high school, but because his role is written with a minimum of dialogue, Martin found herself doing a lot of the talking, and Becca — bright but not bookwormy, generous, wry, and endearingly impatient — soon became more prominent. ”Toward the end of last season, I was getting a lot more to do,” says Martin, who has been acting since she was 7. ”They had written so many scripts for Chris that they had to give him a break.”

According to executive producer Michael Braverman, Martin handled her increased responsibilities without flinching. ”We saw her grow up right on ^ screen,” he says. ”She was a complete professional.”

With Corky’s and Becca’s mother (the pregnant Patti LuPone) bedbound for several episodes this season, the show is relying even more on Martin. The prospect doesn’t seem to worry her, but she does admit that Life Goes On‘s first year was stressful. When she learned she’d be acting with Burke, she says, ”I was really nervous. I’d seen a documentary on Down’s syndrome children in mental institutions, and I thought, How is this going to work? But the second I met Chris, I wasn’t worried. He’s an actor, he loves what he’s doing, he works incredibly hard, and I love him. I feel like his sister.” Shooting was often difficult, but Martin minimizes the problems: ”Some days he just can’t remember a line. But nobody can expect perfection. I’m like that too — I have days when I’m a little spaced.”

By last spring, Martin couldn’t afford to lose her concentration for a minute. ”I was just work, work, work, and study, study, study,” she says. ”I would never say to the producers, ‘Write me less.’ I loved those stories. But when I was getting up at 6 and doing the series and my first year of high school (she is tutored several hours a day on the set), I had gotten to a point where I wasn’t very happy.”

Martin is taking her role more in stride this season. ”I have to remember I’m still a kid, no matter what. I’m with adults constantly, so it can be hard. Sometimes I think about high school — maybe I’m missing having a boyfriend on the football team and being a cheerleader. But I see my friends every weekend and I call them all the time.” She unwinds by exercising (”Jane Fonda, every night”) and tearing through a library that even Becca might find daunting: A recent favorite was Wuthering Heights. ”I know there’s still going to be life after this show,” she says. ”My mom has always said, ‘You can work until you’re 20 and then go to college,’ and that’s what I want — to go to Yale and live in Connecticut and act at night.”

This year Martin has traded in the cherry-framed plastic eyeglasses that endeared her to thousands of bespectacled young girls for a ”slightly hipper” wire-rimmed pair. ”I used to go around blind because I thought only nerds wore glasses,” she says, ”and then I thought, Hey, they’re a fashion statement.” Becca is growing up in other ways as well. ”She might have to deal with drinking, and she might learn to drive,” Martin says. ”The writers come up with great situations because she’s intelligent — it’s so much more fun than playing an airhead. Sometimes I think, How does she come up with these great comebacks every time?”

Martin doesn’t know whether more TV romances await her, but if heartache is in store, she’d like to work on her one acting weakness: crying. ”It is so hard!” she says. ”Viveca Lindfors was on the show, and she was a faucet. They’d say, ‘Viveca, cry,’ and she’d just bawl. It’s one of the tougher things for me. ” I had one director who said, ‘OK, Kellie, when I say action, cry.’ I said, ‘Excuse me?’ She said, ‘Cry.’ I wasn’t going to say I couldn’t, so I guess I did. But it doesn’t come easily. What can I say? I guess I don’t have a lot to cry about.”