As teachers of reproduction, the Planned Parenthood Federation of America has few peers. As counselors in sexuality, it has few ideas.

Nowhere is the difference better seen than in "Teensex? It's Okay to Say NO WAY." Last week the federation announced that the pamphlet has become a "best-seller," with 1.5 million copies distributed since publication in 1979.

No one can quarrel with the pamphlet's effort to "allay the hesitation and fear some teen-agers feel about saying 'no' " to sex. And no one can deny that the high rates of teen-age pregnancy, abortion and venereal disease have created a chaos in which it appears, as one social observer noted, "Our biological drives are several million years older than our intelligence."

The intellectual failure of Planned Parenthood is that it provides no moral context for the discussion. The ethical teachings of history's moral leaders on promiscuity are ignored. Instead, teen-agers are spoken to in pitter-pat. The federation counsels them not to be taken in by the line "C'mon, everybody's doing it." They are told the "only question is: What's right for you?" They are advised that sex won't cure loneliness, prove independence or increase popularity.

But they aren't given moral guidance--that sexual looseness violates moral codes representing the collective integrity that has endured throughout history. They aren't told that chastity and abstinence for adolescents are values honored in all the world's major religions.

That groups like Planned Parenthood avoid the moral context of human sexuality is an easy out: the kids might call us prudes, they might tell us to peddle our Victorian hangups elsewhere.

Such hesitation vanishes when we tell the young that it is morally wrong to shoplift, to take drugs or to cheat in school.

Schools and public service agencies that don't hesitate to impart these value-laden strictures lose their nerve in sexual education. Some schools see themselves as forward-thinking merely to be giving courses in sexual technology. Others go further and join the Planned Parenthood effort to provide value-free counseling.

But it's not enough. It leaves the young floating free. One way or another, they are being sexually educated all the time--at the magazine rack, by films and television, by advertisements that depict Joe Namath or Brooke Shields hawking suggestiveness.

With human sexuality being "taught" in this kind of cultural explosion, the chances increase that the young will make sexual decisions based on ignorance. If a group like Planned Parenthood, which puts itself forward as an "advocate of reproductive rights for everyone," is tepid about discussing moral codes, the young are that much more vulnerable to reactionary moralizers at the other extreme. These are the book-banners and finger-pointers who in their Thou-Shalt-Not crusades offer nothing more than railing against America the New Sodom and Gomorrah.

Caught in the middle and supported by neither the pamphleteers of Planned Parenthood nor the New Puritans passing their "family life" laws, are educators like Mary Lee Tatum. For the past nine years, she has been teaching a seminar in human sexuality within a value framework at George Mason High School in Falls Church. "The students really want to talk about morals and values," she says. "They are eager to discuss why they do things and the consequences of their behavior, romantic and sexual. In the classroom, I try to create an excitement about developing one's values.

Every high school in the country should have a teacher like Mary Lee Tatum. She understands that a moral perspective is as needed a form of prvention against unwanted pregnancy and venereal disease as a knowledge of birth control, fertility and anatomy.

For the unmarried young, it's okay to say "no, it's morally wrong."