At 7 o'clock in the morning, on the day of her Sweet Sixteen party, Christa Brooke Camille Shields pokes the world's most perfect face out from her bedroom in a New York City apartment and yells:

"MOM, do I have to wear my CALVINS today because I'm doing an interview?"

Like Shields herself, the cry lands somewhere in a vaguely defined buffer zone between innocence and pragmatism, with absolutely no mercenary overtones. At mid-adolescence, she is not what she appears to be. Sixteen going on 9 seems a good place to start. And don't believe for a minute that nothing comes between her and those Calvins. The Calvins come between her and her horse, which she would much rather ride than kiss boys. And when it comes to kissing boys, nothing inside. "No butterflies," she says. "Maybe if I had a boyfriend, but I don't."

So what about the child whose she played in "Pretty Baby," and the water nymphet in "Blue Lagoon," and the sexually advanced teen-ager in the forthcoming "Endless Love," just awarded an X rating, which means that Brooke Shields can't go see herself in the movie?

"It's just acting," she says.

Maybe it is. Listen to 20-year-old Chris Atkins, who played opposite her in "Lagoon":

"There was this one shot when we were supposed to be making out and the director said to me, 'Okay, I really want you to kiss her this time.' So I decided to stick my tongue in her mouth, and she jumped back and said, 'Yeeccch! What are you doing?'"

Listen to Franco Zeffirelli on the problems of directing her in the sex scenes for "Endless Love":

"Some women have so much experience that you begin to direct them and they cut you off and say, 'I know what you want, Franco.' With Brooke I have a goddess of purity, a 16-year-old virgin, and I say, 'I want to see passion and ecstasy on your face,' and she shrugs her shoulders. And so I want to say" -- and here the 58-year-old Italian director gives some rather specific ideas of what he would like flowing through her head as she plays scene -- "but there is no way you can say that to her. She is too innocent, too sweet. I would be embarrassed. And then she won't do the nude scenes, so we have to use a body double. It is frustrating. But she is such a specimen of human beauty. I have never looked at a more perfect thing through a lens. I kept looking for flaws and I couldn't find any."

The face is enough to make an alabaster sculpture weep. Why do they ever put makeup on her? The skin looks so creamy rich, the consistency of a thick peach milkshake. The eyebrows fluff perfectly. The hair is the mane of the finest show horse. All of this is perched atop a straight, thin body that stands, when last checked, at 5 feet 11 inches. (She may have grown over the weekend.) She was asked to be on the cover of Sports Illustrated's infamous bathing suit issue. "No way," she says, pulling out the front of the pink polo shirt she's wearing. "Nothing up here." When she walks, the horse imagery returns: a gangly colt, with a penchant for tripping over its own feet. "No way," says her 47-year-old mother, Teri Shields," for Brookie to do runway modeling."

They are an odd couple who have endured much, and if anything ever intruded on Brooke Shield's tranquil sense of innocence it was dealing with her mother when she was an alcoholic. "Let's just say it was a tough period," says Teri Shields, who raised her daughter almost singlehandedly. (She and her 6-foot-7-inch husband Frank -- the son of the tennis pro -- were divorced a few months after Brooke was born.) "I think we resolved that issue [alcoholism], and then Brooke hit puberty just as I was going into menopause and we had something in common to deal with: female sexuality.

"She's a good girl, a kind girl. She has four adopted stray cats. She'd like me to adopt a baby so she could help raise it. I'm madly in love with her and I'm tough on her, but not as tough as she is on herself. That may be a result of having to rely on herself so much when I was impossible to deal with. Brookie says that sometimes she feels like she's the mother and I'm the daughter. I love punk rock -- Devo -- and she listens to the Beatles and Tom Jones. The other night I had to borrow $10 from her to pay for dinner."

Right now Brooke Shields is being driven to school in New Jersey, where her mother takes her every weekday. Brooke is drinking a cup of coffee and eating a bagel and -- whoops -- the coffee is now in her lap, all over the olive green jeans that are not Calvins. Tonight is the big party, for which her mother has rented Regine's, the trendy New York disco. Brooke wanted to wait until after school was out to have the party. She said she wanted the time for studying. Mom persuaded her to take one night off.

She is studying French, algebra, English and biology this year. She hauls around a canvas book bag that must weigh at least 20 pounds.

"I like biology a lot," she says."I might want to be a vet when I grow up."

WHEN I GROW UP!!!!!!!!!

Sixteen going on 9. The girl who fascinates young men and old men and young women and old women . . . and she doesn't think of herself as a grown-up. "It's not really work," she says. "Doing photo sessions or making movies is sort of fun."

"A lot of times," she says, "I work after school. I'll get picked up and go off to a session. I guess it's different than most of my friends at school. A lot of them are looking for work. A few of them are at Haagen-Dazs. What a great job."

Brooke Shields earned a half-million dollars for just six Calvin Klein jeans commercials. Then there were the Wella Balsam ads and the covers of Vogue and other little odd jobs that all together earned her well over a million bucks last year. She knows how to save taxi fare receipts for her accountant.

"I really don't think she's that concerned about her money," says Teri Shields. "She knows that her money is being put away for her. A lot of the things other kids would have to save up for she can go out and get, like a pair of jeans, and they cost 50, 60 bucks. And her horses are fed and boarded. But, believe me, there are kids in school with her who have and spend a lot more money than she does."

She gets an allowance of $10 a week.

Two weeks later she is in the midst of a photo session, where between takes she discos around to an unheard rhythm, like an awkward adolescent girl practicing her dance steps.She ruins plenty of shots by pursing her lips in a ridiculous vertical format. The photographer is asking her to hike her skirt up and pull her blouse a bit off her shoulder. She does it, but instinctively keeps pulling the blouse tighter and squeezing her legs together to cover any embarrassing adolescent flesh that might be poking through where it shouldn't. It's almost inconceivable that this is the same girl who caused such a fuss with "Pretty Baby," which to some was pivotal harbinger of lollyporn. It put Brooke Shields in the public eye, and fan letters started pouring in -- now 2,000 a week.

"Most of them are very nice, usually photo requests," says Teri Shields. "There are some crazy ones. If it's a really rotten one from a kid, I'll call the mother. The mother says, 'I had nothing to do with that letter . . .' and I say, 'My daughter is a very nice girl' and then I put Brookie on. The apology usually shows up in three days.

"People were so upset by 'Pretty Baby.' I told her the story exactly before we got involved and we discussed it with Louis [Malle, the french director]. First of all, the way continuity is on a film, she didn't have to deal with anything when it was being made. When she saw the movie she said, 'I don't think this is so bad. These women are surrounded by heartache and poverty and they have nice clothes and food and a roof over their heads.' And I'm not sure it's good for kids to live in some fantasy world totally removed from the world. She's capable of understanding a lot."

Brooke Shields got into the modeling business at a very early age -- 11 months. "I was involved in the fashion business at the time," her mother recalls, "and Francesco Scavullo called me up. He was sitting in the studio with 300 screaming kids and he had to shoot an Ivory Soap commercial. You can't imagine anything worse than Scavullo surrounded by screaming kids.So he asked me to bring Brooke over -- he knew her -- and we made $35."

A few months later Teri Shields was strolling down 52nd Street with her 18-month-old daughter in a carriage. Brooke pointed at a woman walking down the street. The woman looked at Brooke and looked at Teri Shields and patted the baby on the head. She smiled and didn't say anything and walked away.

Recently, Christa Brooke Shields was confirmed by a Roman Catholic bishop. She chose Camille as her confirmation name. It is from the film she would like to remake in homage to the woman who patted her on the head: Greta Garbo.

"Brooke is really a devout Catholic," her mother says. "She goes to mass and receives communion every Sunday. Her name is a little unusual. When she was going to be baptized I told the priest that I couldn't find the name of a saint I liked. I said, 'What could be better for a girl than Christ with an "a" on the end?'"

Christa Brooke Camille Shields says some of her friends have been asking her how "Endless Love" could have gotten an X rating.

"None of that sex stuff is with me," she says. "I don't know what the double did. I think they should take out the scenes. I don't think these scenes are needed. Anyway, the kids don't bother me about it. I'm just like everybody else here."

Sort of. One day, not too long ago, John Travolta called Teri Shields and asked if he could take her daughter out to dinner. Ordinarily Brooke is not permitted to go out on dates.Ordinarily, in fact, Brooke Shields is not interested in going out on dates. ("But John Travolta," she sighs, as if he is better looking and better known than she is.) And ordinarily -- and absolutely -- she is not permitted to drive in cars with her friends, at least not until she is 18.

But John Travolta is an exception. He pulls up outside school. They drive off to a restaurant. They eat dinner.

And she says, "Now you better take me home," where she arrives at 10 after 7.

"I really had to study," says Brooke Shields."I had a big test the next day."