There is a tendency, among liberals, to cast opponents of public-school sex education into the same bag as book-burners, creationists and religion-in-school advocates.

Obviously some people subscribe to all these things. But it occurs to me that one can have reservations regarding sex education, as it is frequently handled, without being automatically eligible for membership in the Flat Earth Society.

Like my liberal friends, I have trouble understanding people who seem to suppose that sexual ignorance helps to promote chastity. Like my conservative friends, I have trouble with the notion that sex education can be properly taught without also teaching at least the rudiments of morality.

I'm not talking about the biology of human reproduction, which clearly can be taught in a morally neutral context. Schoolchildren ought to be taught "where babies come from," how they develop, and so on. But I have grave doubts about the wisdom of teaching teen- agers about their own sexuality without teaching them something as well of the morality of sexual activity.

I count one-and-a-half arguments against the teaching of morality in the public schools. The one is that morality is indistinguishable from religion and, as such, has no place in the public schools. I suppose I would buy the argument if I knew of religions that advocate promiscuity or theft or murder or the other things that the society generally considers immoral. But it seems to me that there are moral precepts that are held by adherents of all faiths--even by agnostics and atheists--and that these include strictures against adolescent sex. I find it hard to imagine a reli- gious group that would be offended by a public schoolteacher who told her students that it was better to postpone sex until marriage.

The half argument is that a particular class may include children whose own parents were never married and that it is, therefore, not possible to describe premarital or extramarital sex as immoral without condemning the parents of these children. But we are talking moral advice, not condemnation, and my guess is that even unwed parents would prefer that their children postpone sexual activity at least until they are mature enough to handle it.

In short, I don't see moral instruction as offensive to anyone. On the other hand, there are those who clearly find much of our public- school sex education offensive. The mystery is that so many intelligent people find this surprising.

I have a question for them. Suppose they learned that their adolescent sons had a public-school unit on shoplifting. Suppose that the teacher described in full detail the mechanics of shoplifting and also spent some time talking about its legal penalties, all without offering any moral judgment as to whether shoplifting was right or wrong. Now suppose that the final segment of the unit dealt with techniques for avoiding the consequences of shoplifting. ("I leave it to you to decide whether shoplifting is something you want to do or not. But if you decide to shoplift, here are some ways to avoid detection. This method is 94 percent effective, while this one is 89 percent safe.") Would they consider that a good thing?

Well, it strikes me that that comes close to the way some of our sex-education courses are run: no moral judgments as to whether adolescent sexual activity is right or wrong, only instruction in sexual techniques, including techniques for avoiding the consequences of sex.

Amoral instruction on a fundamentally moral issue may offend and frighten the bookburners, the creationists and the Flat-Earthers. It offends and frightens me too.