Chris was 17 when she signed up for a sex education course at her Fairfax County high school. She had been having sexual relations with her boyfriend several times a week for months, and wanted to learn about contraceptives.

By the time her school got around to offering its approved four-hour course on sex, Chris was no longer interested. She was pregnant.

Even if she had been able to attend the sex course, it probably would not have helped. Fairfax County teachers are forbidden to mention contraception, the subject Chris desperately wanted to discuss.

"Sure I was stupid and I should have known," acknowledges the attractive, brown-haired teen-ager as she sipped beer in a suburban pizza parlor. She says she did not practice birth control because the people who told her about sex -- her peers -- had warned her that all the methods could cause cancer.

"But how could I know?" she asks in puzzlement. Reared in a strict Roman Catholic home, Chris says she had never discussed sex -- much less birth control -- with her parents.

"If the school had been there to tell me about it, probably I wouldn't have gotten pregnant," Chris says bitterly. Using money obtained from her boyfriend, Chris cast aside her religious scruples and ended the pregnancy in a Northern Virginia abortion clinic.

Despite numerous statistics showing a sharp increase in the number of teen-agers engaging in sex, educators in Fairfax County -- and around the nation -- are proving as reticent as Chris' parents about discussing the subject.

Educational researchers report that more than 90 percent of the nation's school systems, along with Fairfax County, have placed rigorous restrictions on sex education courses. In most, students are given a week or less of what passes for a sex education course but in reality covers only basic anatomy.

Fairfax County's program, while similar to one in Alexandria, contrasts sharply with those of Falls Church and the District of Columbia. There, students are provided a wide range of information -- including specifics on birth control. "If they ask anything, we'll talk about it," says Falls Church sex instructor Mary Lee Tatum, who has brought contraceptives in to her classroom for students to examine.

Arlington and Montgomery counties, while forbidding teachers to initiate lectures on some subjects, do permit discussions if the student request it. In Prince George's County wide-ranging discussion is permitted, provided students have signed permission from their parents for the class.

Although many educators say the restricted courses reflect the requests of parents who believe sex education belongs in the home, recent polls show most Americans favor more detailed courses. Pollster George Gallup reported two years ago that 90 percent of American adults believe their children should be taught about sex in school, and 70 percent said explicit information on birth control should be given students.

In Fairfax County, in what is often called one of the most progressive school districts in the county, teachers face what appears to be the most restrictive sex education program in the Washington area. Teachers may not mention birth control, or any of the other topics that make up what instructors derisively call "The Big Four" -- abortion, contraception, homo-sexuality and masturbation.

Created in 1976 as the result of pressure from conservatives, religious activists and antiabortion groups, the Fairfax sex education policy also limits teachers to an established script and prohibits them from answering any student questions that touch on topics not covered in teacher curriculum guides.

The result is a program that often is as frustrating to students and teachers as it is pleasing to conservatives. "I could learn more by reading McCall's magazine and the Encyclopedia Britannica," complains Scott Innis, a Mount Vernon High School senior who is one of many students agitating for a chance in the policy.

Partly because the courses are so restricted, few high school students take them. Only 2 percent of Fairfax's high school seniors sign up for the course each year.

A teacher in the Vienna area, who declned to let her name be used for fear she would be fired, said the sex courses were so watered down that they were pointless.

"We're failing these kids -- we're actually doing them harm," said the teacher, who teaches the high school course each year. "We don't give them the opportunity to discuss things seriously with one another, or hear the other side on dating and values."

Barriers to sex education bear grave consequences, say health experts, pointing to rising rates of veneral diseases among area teen-agers.

"When you try and hide things from kids, you're just increasing their chances of health problems like VD, unwanted pregnancies and possible cervical cancer," Said Jeames Ludwig, who monitors Northern Virginia for the Center for Disease Control in Atlanta.

Fairfax County is about to reevaluuate its program, but, conservatives there are lining up to preserve the status quo.

The Most Rev. Thomas J. Welsh, Catholic bishop of Arlington, has called on parents to vote against more detailed courses, arguing that discussions about sex belong in the home. Any public discussion "would be an invasion of the scared right and duty of parents," he said recently.

Elizabeth Burch, who operates a Fairfax bookstore, franchised by the John Birch Society, is leading a group called the Movement to Restore Decency (Motorede) to kill any form of sex education in the Fairfax schools. d

"children are always taught to do their homework in school," said Burch. "So when they're taught about sex, they'll want to do their homework, too."

"We feel that when the body is ready for sex, the students will naturally know about it."

At the center of the storm in Fairfax is an optional, four-hour course presented to students at elementary, junior high and senior high levels.

In classes segregated by sex, students watch films that focus largely on human physiology. Only approximately 10 minutes per day is set aside for discussion, with teachers required to follow established script.

"We feel our hands are tied," complains Vivian Sins, who supervises the corps of nurses assigned to Fairfax schools. "We can reassure them [the students] as much as possible and if they show visible signs that they're aborting, we can treat it," she says. "But other than that you just can't talk about it -- even in the parking lot . . . . It just makes you feel terrible."

According to a PTA committee, questions that went unanswered at one Fairfax junionr high included:

"What do you do if the boy wants to have sex and you don't know how to tell him 'no"?

"How old do you have to be to use a tampon?"

"What makes most females worry about pretty stuff and makeup and boys like sports and dirty clothes?

"Can you get pregnant from oral sex?"

Even a film on veneral disease did not escape Fairfax's rules. Although the film, shown to high school students, includes information on the symptons and remedies for VD, school officials confirmed that a reference to prevention through use of condoms was edited out beacuse condoms can be used for birth control.

The program at nearby George Mason High School in Falls Church by contrast offers a no-holds-barred approach that has won much national acclaim. It recently was chosen by Colubmia University to serve as one of five models for sex education courses around the country.

According to Dr. Susan Philliber, who conducted the Columbia study, the Falls Church program is "registering clear gains in terms of student knowledge and in promoting parent-child communication about sexuality issues."

The theory behind the program, says theacher Mary Lee Tatum, is to give students solid information and a reasoned forum in which sex can be discussed with their peers.

The result can be compelling for the students, unlike the Fairfax courses. A recent Tatum class, composed of an equal number of boys and girls, refused to leave when the final bell of the day interrupted their discussion of sex roles.

Tatum's courses, which include a full year of instruction for ninth-graders and a one-quarter course for seniors, represent what she calls an effort to get teen-agers to "talk seriously about sex.

"If they talk seriously about it, the chances that they'll make better decisions are much higher," says Tatum.

What is improtant, Tatum says, is that her students learn that sex, love and interpersonal relationships are not "something mystical," but an integral part of each person's life. Although Tatum's courses are offered as electives, more than 90 percent of George Mason students take them.

"Since I've been in here [the class] the boys seem more like people -- not just big macho guys looking for sex all the time," says Jill Waite, a freshman.

David Rodgers, captain of the school's football and wrestling teams, says the course has made him feel more rsponsible about birth control. Rodgers, a senior, estimates that more than 60 percent of his classmates are sexually active.

Spontaneity (sex without birth control) is just a "luck scene" he said. "if you don't want to use birth control, that's just your option."

In the end, the amount of sex education a student receives may be irrelevant. As Maureen, a pretty blonde senior as a high school in southern Fairfax County, sees it the risk may be to save their reputations even if it means getting pregnant in the process.

"You really can't go out with a lot of boys in high school anymore, because people will call you a slut or a sleaze," says Maureen, who wears her shiny hair in shoulder length curls. "So you end up going out with only later."

But because she wants to avoid being viewed as cheap by her boyfriend, she hasn't dared discuss birth control with him. "He's got me up on a pedestal," she says. "Somehow discussing birth control doesn't fit in with the mystique."

The county also is likely to impose special safety requirements on Bowman to assure that the distillery's shift to 190 to 200 proof ethanol will not endanger area residents. Wessel said. The plant produces bourbon under the Virginia Gentlemen and Fairfax County labels.