SHE IS pale as porcelain, and there are only 94 pounds on limbs that look as light as a lyric, but the punishment they take is more tuned to the expectations of an athlete than an artist.

"She was born a dancer -- dancers are born, you know," says her mentor, Mary Day, director of the Washington School of Ballet. "There's no limit to what she can expect."

In June, Amanda McKerrow can expect to go to Moscow, to compete with nine other dancers as a member of the American team in the International Ballet Competition there. Only 17, she won a place on the team last week in the regional tryouts in New York and will be competing on what amounts to Olympic levels in the dance world. So there was much jubilation sounding in between the patient piano chords accompanying the classes rehearsing the afternoon away.

"I was happy I won, but not as happy as I thought I would be," she says as she sits curled in a graceful filigree in one of the school's sparsely furnished dancers' lounges. "I still have to satisfy myself."

She wants -- well, it is hard for her to say what she wants; dancers' dreams are best kept hidden from the hand of fate. "I'm ambitious," she says cautiously, "but I know I'm not going to be another Makarova." A pause.It is not, at least, something to admit to out loud. "I'm also superstitious," she says, knocking on her wooden chair. "I'll take it as it comes."

McKerrow, who was born in Albuquerque, N.M., lives at home in Rockville with her parents. She began dancing when she was 6, after an older sister began taking lessons. By the time she was 12, she knew that she wanted it to be her whole life. At 12, after all, doubt is a word with very little leverage, and she had no doubts. She started as a student with the Washington Ballet School two years ago, worked her way up to the level of "aspirant" last year and now is a full-fledged member of the company.

"I knew I wouldn't be happy doing anything else," she says. "I'm basically kind of a shy person, but when I dance, I don't feel that way at all. I know some people have the kind of jobs that they start at 9 and leave behind them at 5, but I could never do that. I think about dancing all the time."

She is such a young ballerine, after all, and there has been very little time for the quandaries that come from hard turns taken and roads forsaken. Her life is lit by promise, undimmed by any of the disappointments that can shadow the sheer simplicity of grace in motion.

She dances up to 12 hours a day, six days a week, and with such dedication that there have necessarily been certain activities discarded along the way. Traditional schooling was among the first to go -- she left Rockville High after her sophomore year, and with the aid of an understanding guidance counselor and the signing of the necessary forms, took correspondence courses from the University of Nebraska to complete her junior year of high school. This year she decided the five courses she would have to take would mean too much of a sacrifice from her dancing, and decided instead to study for the exam that would qualify her for the Graduate Equivalency Degree to complete her education.

The usual high school social life, with its awkward Saturday night pas de deux, has been put in suspended animation with little regret. "I guess I'm giving up stuff like the weekend basketball game," she says. "But I don't feel like that's giving up a lot." In her off hours, she likes to do the kinds of things that would seem more mundane in a less secluded life -- going shopping, for instance, or fixing up her room at her parents' home.

"We're behind her 100 percent," says her father, Alan McKerrow, an administrative officer with the National Institutes of Health. "At first, we were a little nonplussed by it all, frankly -- she's our last child [of four] and every parent wants to see their child finish school. But we've never had a child so dedicated, so determined in what she wants to do. We feel that if she loves it so much and it means so much to her, we want to help her every way we can."

The trip to Moscow will be Amanda's first time out of the country, but now her first experience with the harsh strains and pressures of competition. Last year she came in second in the finals of the National Society Arts & Letters ballet competition and danced before Balanchine at the banquet celebrating the winners.

"Competition involves a different kind of nervousness than performing," she says. "I'm not real fond of it. A performance you do for yourself and for your audience; there's a lot of enjoyment in it. But in a competition, one small mistake can make a very real difference. You get nervous, but you know you can't get nervous, you have to concentrate. You try not to think how impossible it is. Somehow, your body just keeps on moving -- you hear the counts and see the steps, even when you think you've forgotten."

Like a hot pitching prospect or a star high school quarterback, McKerrow is aware of the scouts from prestigious ballet companies who come to competitions and performances to look her over. This winter, she heard rumors that Baryshnikov had sent two emissaries to a performance of the "Nutcracker" in which she was dancing; but if the observers made it, she did not, having been felled by an untimely attack of the flu. There will be more such messengers in Moscow, but she approaches those prospects in a measured way. "I really don't have any idea of what could come of it," she says. "I'm just going for the experience."

She skims along quietly on the surface of her self-confidence, her dreams cloistered in the discipline demanded by her art. So far, she has been lucky -- there have been few injuries to interfere with their realization. bStill, she doesn't like to dwell on the damage that could be done, at any time, and in that she says she identifies closely with athletes. "You never want to go to a doctor," she says. "Because you don't want to think about what you would do if they said the words, 'Stop dancing.'"