COLUMN ONE : When Sex Just Isn’t Worth It : With the AIDS scare, there is a renewed call for abstinence. Most teens are not convinced. But a defiant minority cite fear of pregnancy, disease or parental disapproval.

Carlos Collins, an 18-year-old college-bound senior at George Washington Preparatory High School in Los Angeles, tried sex when he was 16. Now, he is into no sex.

“As a matter of fact,” said Collins, “me and my friends are kind of abstinent because we know about the horrors that are out there, like AIDS and everything. I have some friends who are into one-night stands, but that is not my style. To me personally, it’s not worth it.”

Nkechi Obioha, a 16-year-old student at the Los Angeles Center for Enriched Studies, is curious about sex, but not ready. She wants to attend Harvard University, and a sexual relationship would complicate an already full life.

“I have told myself that I will make up my own mind when I am ready to have sex. No one is going to pressure me or tell me when,” said Obioha. “If you are sexually active, the chances of your getting pregnant are higher, and that is something that can take you out of the education arena. And education is the No.1 thing at our school.”

Unusual views? Definitely. By the time a teen-ager reaches the 12th grade, he or she is far more likely than not to have had sex. According to a study released Friday by the national Centers for Disease Control, 54% of American students in grades nine through 12 have had sex--and seven out of 10 high school seniors.

So why would a teen-ager choose abstinence?

Fear, primarily. Fear of pregnancy. Fear of sabotaging career plans. Fear of emotional upheaval, of AIDS and other sexually transmitted diseases, or of parental disapproval. (On the other hand, a few teen-agers say that they have never been asked.)

On Nov. 7, the issue of abstinence captured national attention as never before. That was the day Earvin (Magic) Johnson announced that he had tested positive for the AIDS virus. The avalanche of publicity that followed focused initially on safe sex. But before long, voices--including Johnson’s--began trumpeting abstinence as the only safe option.

“Young people especially have to think more carefully about the decision to have sex, because the ‘safest sex’ is no sex and that is really the most responsible choice,” Johnson said 2 1/2 weeks after his dramatic retirement.

Whether adolescents will take that message to heart remains to be seen.

In general, researchers say, a fairly predictable line can be drawn between those teen-agers who have sex and those who abstain. On one side: low-income teen-agers, teen-agers without educational and career aspirations, teen-agers whose parents are not actively involved in their lives. On the other: highly motivated, college-bound teen-agers who understand the trade-offs of early pregnancy and disease.

“I think there are some very clear-cut class or aspirational biases in all this,” said Gail Zellman, a RAND research psychologist who specializes in youth policy issues. “Kids who don’t perceive much hope for the future just don’t have the incentive to think ahead. I don’t think they think they can control that element of their life very much. If girls have a guy they like and who is pushing them, then, you know, eventually they probably give in.”

A 1988 study of single 15- to 19-year-olds by the Alan Guttmacher Institute, a New York-based group that studies reproductive issues, found that sexual activity varies by race and ethnicity: Among males, 19% of African-Americans, 40% of Latinos and 43% of whites have not had sex. Among females, 41% of African-Americans, 53% of Latinas and 52% of whites have not had sex. The CDC survey, conducted in 1990, yielded similar results.

But Dr. Bob Blum, a professor of pediatrics and director of the division of adolescent health at the University of Minnesota, cautions against drawing hasty conclusions.

“It sort of implies that these aren’t behaviors that are prevalent among the white middle class,” said Blum. “They are very prevalent.”

Though fear of AIDS is sometimes cited as a factor, for the moment, it appears not to be the main reason teen-agers abstain. Most still consider it a disease someone else gets. Pregnancy is a greater worry, as is emotional upheaval. Many teen-agers who abstain think that they are too young to have sex.

In 1989, Blum released the results of a Minnesota youth health survey in which 36,000 12- to 18-year-olds were queried. A number of questions focused on sexual behavior--including abstinence. Blum discovered that girls were far more worried about pregnancy than boys; both sexes worried equally about sexually transmitted diseases. Further down the list of reasons for abstinence were “haven’t met the right person” and “my parents’ values are against it.”

Parental values, though not paramount to either sex, emerged as far more important to girls than boys--about 25% vs. 10%. Some adolescents said the reason they have not had sex is that no one asked them.

Seventeen-year-old Catherine Kim feels she is swimming against the sexual tide. A senior who attends the humanities magnet at Cleveland High School in Reseda, she senses that her peers think that graduating high school without having sex is something akin to a character flaw.

“Sometimes in our journalism class, we are talking (about a classmate) and kids are saying: ‘Oh, she is so frigid, she is never going to be touched!’ Even though it is sort of innocent, the underlying tone is: ‘Oh my God! She’s a virgin. There must be something wrong with her.’ At my school, by 17, everyone has had sex.”

Kim said she has decided to postpone sex, mostly because she fears pregnancy, but also because she was upset when a girlfriend contracted a sexually transmitted disease last year.

“After that,” she said, “it really hit home. I never met anyone before who was sick from sex. Sometimes, I think: ‘Oh God, I really wish I could experience it.’ I really am curious. But it’s too scary.”

Eshauna Hicks, a 16-year-old student at Hamilton High School, said the subject of sex comes up with every boy she dates.

“All boys bring it up, but it’s not like an ultimatum,” she said. “They are like: ‘When are we going to have sex?’ But I just want to wait, personally. Most of the time, I just change the subject, but if it is someone I care about, I tell them how I feel. I have a boyfriend now, sort of, and I said: ‘I am not ready,’ and he said: ‘OK.’ ”

Hicks and others who opt for abstinence sometimes cite younger siblings as part of their motivation.

Obioha has a sister who is 12 and a brother who is 7. She has experienced firsthand the tremendous demands of babies.

“When I was 5, I was changing my little sister’s diaper, and when I was 10, I was changing my little brother’s,” she said. “They are not my kids, but I feel like I’ve had my own babies. And I consider myself very responsible. It would be so unfair to bring children into this world and not be able to take care of them.”

Hicks said that most of her friends are having sex, but she wants to be able to set a good example for her little sister.

“I want to be able to tell her I waited until I was ready,” said Hicks. Besides, she added, “I want to do something with my life.”

The old double standard also seems to keep some girls lined up on the side of abstinence.

Rhiannon, a 14-year-old who did not want to give her last name, said: “I think it’s stupid to ask kids not to have sex. It’s just stupid bureaucratic people who want that to happen because they have their own ideas.” Nonetheless, Rhiannon said, she is not ready for sex--and she is well aware that teen-age girls who have sex are often considered cheap.

“There is a girl at our school and all her friends are boys and she gets drunk and goes off with them and has sex with them and people tease her so much,” she said. “I don’t think she is thinking about the price she will pay for this, she is just thinking of having a good time.”

Likewise, a pair of ninth-graders at the girls-only Marlborough School said their classmates who have sex are considered “sluts.”

“It’s not normal for girls to have sex,” said one. “For boys, it’s something to brag about. For girls, it’s something to worry about.”

Is there any connection between sex education for teen-agers and abstinence? In Los Angeles, parents, educators and community activists are engaged in a raucous debate over one component of a sex education plan that would allow the distribution of condoms in secondary schools. Some of the most vocal opponents say giving an abstinent teen-ager a condom tacitly encourages sex.

But researchers say that there is no evidence to support the contention.

“It’s the old argument that if you teach sex education, they will go out and have it,” said Leni Wildflower, a human development teacher at Harvard-Westlake School. “But if you talk and teach concretely about these subjects, kids are less likely to get involved in risk-taking behavior. My own feeling is, you ought to be doing all of it: lots of condom distribution and lots of talking about the value of abstinence.”

Marvin Eisen, principal research scientist at Sociometrics Corp., a Los Altos-based think tank that specializes in youth issues, said some people may conclude that sex education or condom distribution leads to sex because there has been some suggestions that providing drug information may have led some minors to experiment with drugs.

What is clear, he said, is that teen-agers who take sex education courses are more likely to be “better contraceptors” than those who do not.

In a 1985 study of 1,440 adolescents conducted in California and Texas schools, Eisen, RAND’s Zellman and a third researcher, Alfred McAlister, found a possible link between an experimental sex education program and the delay of intercourse for young men.

Among young men who had not had intercourse before participating in the study, those exposed to the experimental program were more likely than those exposed to other sex education programs to maintain abstinence during the next year. There was no discernible effect on young women, however.

The program was based on a model of how people translate their beliefs into behavior. The so-called “health belief model” posits that in order to get adolescents to change their behavior in a positive way, the adolescents must believe that he or she is susceptible to some problem (pregnancy, sexually transmitted disease); must be convinced that there will be consequences (quitting the team, giving up school); must understand that there is a way to prevent the problem (abstinence, contraception), and must be convinced that the psychological or economic barriers they perceive are not as great as they think (buying condoms is easy; it is OK to say no).

The program featured a board game to show teen-agers how susceptible to pregnancy they are.

“We said: ‘Pretend you and your partner are having unprotected sex twice a weekend over the football season,’ ” said Eisen. “We had a board with 15 spots--14 numbers and a smiling baby’s face. This way, we made it clear to them that for any given exposure, there is a one-in-15 or -16 chance you could get pregnant if you don’t know where you are in your cycle. Each spinner spun 20 times--twice for 10 weekends--and more than half of them landed on a baby eventually.”

So why did this program have an effect on the behavior of boys but not girls? Eisen thinks it might be because girls are warned so often about pregnancy.

“Even if girls are not very knowledgeable about birth control, they know more about it than boys,” said Eisen. “One way or another, parents have said something about the fact that girls are susceptible.

“On the other hand, many of the boys . . . were hearing this for the first time. The boys were starting out at such a low level of cognition that anything that got them thinking at all was somewhat helpful.”

Sex--or the urge to have it--is inevitable. Indeed, more teen-agers than ever are having sex. Although there are theories about why some adolescents choose to abstain, there is no easy explanation for why increasing numbers do not.

Beth Frederick, director of communication for the Alan Guttmacher Institute, said hypothetical reasons range from “everything from the media’s portrayal of sex to the fact that a lot of teens live in families with only one parent and they have grown up with their role models having a sex life.”

Collins, the senior at Washington Prep, has steeled himself against those influences and more: “At our school,” he said, “all the guys brag about the fact that they have a girlfriend, and they only want her for one thing: sex. I very calmly ask them: ‘If you are going do that, what is the point of having a girlfriend that you are supposed to love, because sex is not love?’ Their response is: ‘Oh, you aren’t living in the current ages, you should be more sexually active.’ So I tell them: ‘Fine, we’ll play it your way. And when you come up with a disease that leaves you scratching at night, I want you to remember you’re hipper than I am.’ ”