Suppose the question showed up on some national true-or-false quiz. "Is sex education primarily the responsibility of parents?"

The answer would, I'm sure, be a resounding "Yes."

So Richard Schweiker wasn't taking a great risk in his opening salvo against federal funding for sex education. He said simply, "I don't think it's the feds' role to do it." It is rather, he said, the business of parents.

But there was also something false in this reasoning. Something false in the underlying notion that parents have ever been their children's sex educators and that the government, with its host of professionals, took away our job.

In this area, as in so many others, our behavior as parents hasn't met our own expectations. It has never been easy to talk about sex with children. Anxieties and taboos have silenced centuries of parents; our century is not unique. The experts didn't usurp our role. We gave it up.

Parents and teen-agers have long been involved in a mutual "strategy of concealment" about our sexual lives. As recently as 1969, only 13 percent of the teen-agers who went to birth-control clinics had mothers who acknowledged their children's sexual activity.

Even now we are unlikely to actually be the sex educators of our children. In one study, 85 percent to 95 percent of parents of children under 11 had never mentioned any aspect of erotic behavior. In another, only one-third of mothers and teen-age daughters discussed sex or birth control with any regularity.

The people most irate about the "other people" giving sexual values to their children are often the ones least able to talk themselves.

Educators and family planners came in to fill a gap that we left open because of our awkwardness or ignorance. They usually did it with our blessing. In every survey, parents have overwhelmingly supported sex education in the schools.

Now all our qualms are coming to the surface. They are often and understandably aimed at the professional who dealt privately with our children and even identified us, their parents, as the enemy.

As Faye Walleton, the head of Planned Parenthood, now admits: "In the early '60s and '70s, parents became symbolic of the establishment and all that was repressive. We saw our role as being advocates of young people."

The family-planning clinics often dealt with our children as their patients, dispensing contraceptives. The sex educators often dealt with our children as their students, teaching the "value-free" facts. We often felt excluded.

But parents are changing and so are the professionals. We have all become much more aware of the problems of premature sex -- emotional and medical -- from the anxieties about intimacy to the trauma of pregnancy. We have all become more sensitive to children's real needs for guidance and values.

The professionals who worked to make abortion available to teen-agers have become more concerned with making it unnecessary. The educators who worked to answer student questions about sex now try to answer the most common question from girls: "How do we say 'no'?"

It is becoming more obvious to all of us that young teen-agers are still very much a part of family life and that parents still have an enormous influence. The latest research suggests that when mothers do talk to their teen-age daughters about sex (there is almost no one talking to our sons), the daughters may not only postpone sex but are more likely to use birth control when they have it.

There is also solid evidence that parents are dealing more overtly with teen-age sexual activity. Today, more than half of the teen-age girls who go to birth-control clinics do so with a parent's knowledge. t

For all of these reasons, new programs are being developed to help parents deal with these issues. Clinics are learning to deal with teen-agers as part of a family system. Religious groups as diverse as Mormons and Catholics, educators as far apart as Massachusetts and California are beginning to encourage parents to come to terms with their own values and to communicate these to their children.

Professionals have learned, as Ruth McDonald of the Educational Development Corporation says, "There is just no way to deal with teen-agers without dealing with their parents."

We are at a turning point, then -- a moment when federal money can be used to support, not undermine, family life. Silent parents and wary professionals are disengaging from some covert competition over teen-age sexual lives. It is just possible that we can all become partners in caring.