* In Washington this month, Health and Human Services Secretary Otis R. Bowen introduced a series of radio spots decrying the "tidal wave" of teenage pregnancy and urging young people to "develop a more responsible attitude toward sexual relations."
* In New York in April, the national YWCA introduced a be-bopping, hip- wiggling rap-music video titled "It's Okay to Say No Way!" Sample lyrics: "You go around bragging to all your friends/ About all the little chicks that you have pinned. . . . So what's the deal, baby brother/ How many little chicks you gonna make a mother?"
* In Illinois, health educator Coleen Kelly Mast says her phone is ringing ''from early in the morning until 10 at night" with requests for her "Sex Respect" curriculum, which offers "sex education with confidence, not controversy," since it teaches adolescents about sex control, not birth control. "Pet your dog, not your date!" says an illustration in the curriculum guide.
* In Philadelphia this spring, a mayor's panel on teen pregnancy called for sex-postponement instruction for fifth through eighth graders, and public high school teachers this fall will introduce a sex-education curriculum with a beefed-up emphasis on abstinence. Already, local educators, social workers and church leaders are signing up for city-sponsored training sessions that teach them how to use a course called "Postponing Sexual Involvement." When is it OK for young people to have sex? "When they sign that marriage license," says one of the session instructors, Sister Nora Dennehy.
* In cities across the country, instructors trained by the National Urban League are teaching parents to be on the lookout for signs of early sexual involvement - things, a league official says, like short skirts and heavy makeup on their daughters and, in the case of their sons, "tight pants, open shirts . . . and behavior that calls attention to the crotch." The parents are told they should communicate better with their teenagers, but if it takes a firm "No!" to do the job, that's all right, too. "It's such a relief to the kids sometimes," says Urban League project director Eleanore Wells. "(They're telling their friends) 'I can't do this because my mother would kill me.' "
WHAT'S BEHIND IT? Some say the "say no to sex" push stems entirely from the Reagan administration and the nation's conservatives, many of whom may long for the sterner days when premarital sex was considered taboo and teen pregnancy was discouraged - and punished - with forced weddings.
In fact, the Reagan administration is directly responsible for many of the new teen-abstinence programs. The 1981 Adolescent Family Life Act, nicknamed ''Denton's chastity bill" after Senate sponsor Jeremiah Denton (R., Ala.), is awarding millions of dollars in grant money to new projects that will, among other things, try to find ways to get adolescents to postpone sex.
Jo Ann Gasper, a deputy assistant secretary for population affairs who directs the federal office that funds the new projects, leaves little confusion about the administration's intent. "We say no to drugs, to drinking (for young people) - I don't know why we can't say no to sex," Gasper, a Ronald Reagan appointee, said in an interview this month.
Not that sex is "bad or evil or dirty," Gasper said, but it is ''wholesome and so important that you want to wait for the right time." That right time, she added, is during marriage. "The goal of waiting for sex until marriage is a good goal," Gasper said. "It's an appropriate goal and, for most people, a reasonable goal."
Teen-pregnancy experts scoff at the notion that a "wait till marriage" standard could again ever take hold in the sexually loosened-up United States. "That strikes me as sort of absurd," said Frank Furstenberg, a University of Pennsylvania sociologist and teen-pregnancy authority. For one thing, he notes, America's increasing tendency to delay marriage - the median age of first marriage is now 22.5 years for women and 24.4 years for men - makes it unlikely that people will be willing to hold on to their virginity that long.
Just the same, Furstenberg and other experts seem willing to give the "say no" programs for teens a try. One big reason: Years and years of a progressive drive to provide teenagers with the most up-to-date contraceptive information and contraceptive services have hardly made a dent in the nation's teen-pregnancy crisis.
Figures from the National Center for Health Statistics create a dismal picture, indeed. Although the teen birth rate has been going down, numbers are still strikingly high. Teens had close to half a million babies in 1983 (compared with about 600,000 in 1973). Teen abortion numbers are striking, too. In 1981, the most recent year for figures comparing abortions and births, girls 15 to 19 years old had nearly as many abortions (433,000) as they did babies (527,000).
Out-of-wedlock teen child-bearing has become the American norm. By 1983, more than half of new teen mothers were unmarried - compared to an estimated 15 percent of teen mothers who were unmarried in 1950.
And while the marriage age is increasing, factors such as improved
nutrition have caused the age of puberty in the United States to drop over the century - girls begin menstruating now, on the average, at 12 1/2 years and boys begin emission of sperm by age 13 1/2. In contrast to the nation's older single women who fear their fertile years are running out, adolescents are being pushed by a biological time clock with backward spinning hands and an alarm that chimes "do it early!"
A lot are responding to the alarm. Over the decade of the '70s, sexual activity by female metropolitan teens aged 15 to 19 increased by two-thirds, according to New York's Alan Guttmacher Institute, a nonprofit center researching reproductive and sex trends. The institute estimates that nearly half of all 15- to-17-year-old males and a third of 15- to-17-year-old females are having sexual intercourse.
Teen-pregnancy experts complain that the adolescent sex drive is being aided and abetted by the media, which - with its sex-drenched soap operas and glorification of trendy unwed mothers like Tatum O'Neal - are sending a message to young people that unrestricted sex is hip.
"It's so blatant," says George Anderson, a teacher at South Philadelphia High School, who counted 29 teen mothers or pregnant teens among his roughly 130 female students this year. "I can see the difference from when I was in high school," the 38-year-old Anderson said. "I can see the difference in just regular newspaper advertisements for underwear. You know, it's the kind of thing that you used to have to buy magazines, special magazines, to see. . . . (Now) the kids take it for granted. To me, it's erotic. To them, it's par for the course."
ENTER, ABSTINENCE. Alarmed by a high teen-pregnancy rate in Atlanta, experts at Emory University and Grady Memorial Hospital in the late 1970s developed a comprehensive sex education-contraceptive education program for all eighth graders in the public schools. The program worked - but only so far.
"What we found was that we were increasing the knowledge base of these kids but we weren't seeing any behavioral or attitude change," said Marie E. Mitchell, Grady's program supervisor for teen services. "A lot of them were still becoming pregnant. We hadn't seen a significant drop in the number coming to the hospital."
On to Plan B. Inspired by an anti-
smoking program that taught young adolescents how to resist peer pressure to smoke cigarettes, the Emory-Grady team developed a curriculum called ''Postponing Sexual Involvement" for teens under 16. Although most of the nation's sex-education courses have always included an abstinence message, this one was strikingly different. Abstinence was the only message.
The new curriculum said little about the reproductive tract and nothing about birth control. It didn't instruct young people on how to make the right decision regarding sex. Instead, it started with the premise that sex for very young teens is a bad idea. And it taught them the skills to say no.
For instance, a boy might say to a girl: "A lot of your friends are doing it."
And the girl might reply: "What my friends decide to do is their business. I make my own decisions."
Many other sex-education courses are built around a decision-making model that tries to steer teens toward a responsible decision on whether or not to have sex. But Emory-Grady officials, who introduced their curriculum in 1984, believe that young people ages 12 to 16 simply lack the mental capacity to make a decision of such import.
"We don't let 13-year-olds do that with any other areas of their lives," Mitchell, a registered nurse, said. "We don't let them drive by 13, buy alcohol when 13, so we ought to give them this structure in their lives, too."
And while it is true that young people have physical urges to have intercourse, Mitchell said, "it doesn't mean you have to act on them."
Even though the program's success rate hasn't been evaluated yet, interest in it has been "exceptional . . . far beyond our imagination," Mitchell said. Inquiries have come from school districts, churches and organizations all over the United States and from Canada, England and Australia. Between
6,000 and 10,000 copies of the curriculum, which is intended for use with more comprehensive sexuality courses, have been sold.
"I think it's just that our timing was good," Mitchell said. " . . . We have struggled with this issue of teen pregnancy so long that people were looking for something different. And I think the moods and the attitudes of the country are starting to swing back just a little in terms of sexual behavior."
Some creators of other new abstinence programs would like to see those attitudes swing way, way back. Bradley, Ill., educator Coleen Kelly Mast, who is developing her "Sex Respect" curriculum with the aid of a $300,000 federal grant, believes it is time for America to return to a sex-after- marriage-only ideal. "The first 200 years of our country we had traditional values that society supported - wait till marriage - that worked well," Mast said.
Very values-oriented, Mast's curriculum stresses the joys and responsibilities of relationships, marriage and child-rearing. It promotes ''secondary virginity" as a goal for young people who have already had sexual intercourse but want to stop. It says nothing about birth control, the reproductive tract, masturbation or homosexuality. Those matters, Mast says, are best left to the parents.
"This one gives the parents everything," said Mast, who believes her curriculum can serve as a school's only sex-education course. "And if anyone's religion is against virginity, they can get a note to stay out."
Other new abstinence programs are more practical, aiming a "say no" message at youngsters who have not yet become sexually active, yet still offering contraceptive help for those who have.
The Girls Clubs of America organization is among those taking the two-way approach, adding a sex-postponement program called "Will Power: Won't Power" to other programs that talk frankly about birth control.
"A lot of us in the field used to think that sex education was the main way to prevent adolescent pregnancy, and you combine that with access to contraceptive services," said Jane Quinn, Girls Clubs' director of program services. "And then we're all wondering why that didn't work.
"There are a number of people like ourselves, a few of us, who are taking a much more comprehensive and multifaceted approach to the problem."
BUT WILL IT WORK? Some teen-pregnancy experts believe that the new abstinence programs might actually increase the nation's teen-pregnancy problem - by pushing aside comprehensive sex-education programs that provide needed contraceptive advice to youngsters determined to have sex.
If the programs work and "teens stop having sex - that's great," says Susan Newcomer, director of education for the Planned Parenthood Federation of America. "But if the programs become more popular but kids don't stop having sex, then we will have more unintended pregnancies. That I worry about."
Cautions Penn's Furstenberg, who is a consultant on the Emory-Grady program's evaluation: "If you're targeting these programs at kids who have had sex for a couple of years, as sometimes occurs, I don't know that they're going to be effective and they may be counterproductive and undesirable." They may encourage an attitude among young people that " 'premarital sex is wrong and therefore I'm not going to take responsibility for my action,' " he said.
"The attitude of many teenagers (today) is 'it just happened,' " Furstenberg said. "It absolves them of the moral responsibility, but also a lot of the practical responsibility."
Furstenberg said it was too early to determine if the new sex-postponement programs would be successful. But among many teen-pregnancy experts, both conservative and liberal, there is a growing attitude that says, "Let's try it; it wouldn't hurt."
Rita C. Altman, Philadelphia's head of public school curriculum and staff development, is among those who have found some of the existing sex-education programs - with their heavy emphasis on contraceptive information - lacking.
Such an approach, she said, "was too mechanical. . . . It didn't deal with the more basic question of why do you enter into a relationship. And there's the key."
Some of the existing programs also seem to provide little support to the considerable group of teenagers - more than 50 percent by one estimate - that is not having sex at all.
"We were putting so much emphasis on prevention, and people were pushing contraceptives . . . that we weren't looking at that young group of people who make the decision to postpone or wait," said Ella M. Bowen, executive director of Philadelphia's Youth Services Coordinating Office and one of those recommending the addition of more postponement messages. "We jumped to the extreme - contraceptives, contraceptives, contraceptives. And it's more of a values, a change-of-attitude kind of approach we are taking now."
Still, it may be a long way from idealism to reality.
Sol Gordon, University of Syracuse researcher and writer, repeating an observation that has become well-known in sex-education circles, said last week: "I don't think teens should have sex, if the teen is someone under the age of 18 (and unmarried). They are too vulnerable, too readily available for exploitation. They don't use contraceptives. They don't know that the first experience of sex is usually grim. In short, it's a health hazard.
"But in my 30 years of work in this field, no teen has ever asked my consent for having sex."