A few weeks back, the mainstream media were scandalized by a new study showing that abstinence education works. The study found that an eight-hour abstinence course dropped sexual-activity rates among teens by a third, and that the decrease continued two years after the course. By contrast, a “safe sex” program and a third program combining abstinence and contraceptive messages had no effect in reducing sexual activity or increasing contraceptive use.

Abstinence experts weren’t surprised. Eleven prior studies, which the media chose not to report, have shown similar results. The latest study, however, using the most rigorous methods, and published in the prestigious Archives of Pediatric and Adolescent Medicine of the American Medical Association, was too prominent to be ignored.

The claim that abstinence programs don’t work is one of several myths used to attack abstinence funding. In addition, opponents have claimed that the federal government funds only abstinence — but a recent study by the U.S. Department of Health and Human Services found that, even during the Bush presidency, the federal government spent $4 on programs proselytizing for condoms and distributing them to teens for every $1 it spent on abstinence.

Opponents have also charged, falsely, that abstinence education leaves youth ignorant of contraception. While it’s true that abstinence programs as such, allotted little classroom time, do not teach about contraception, in most cases students learn basic information about contraception in other venues, such as a biology or health class.

The rap on abstinence education in the mainstream media has been a smokescreen to obscure the real issue: a clash of values.

This clash has been going on for quite a while. Supported by small amounts of federal funding, abstinence programs gained a toehold in classrooms in the mid-1990s, particularly in middle schools. This outraged the Left, which worried about losing its monopoly over sex ed. At the federal level, Planned Parenthood and Kinsey-inspired groups such as Sexuality Information and Education Council of the United States and Advocates for Youth strove to abolish the modest federal funding for abstinence and replace it with revved-up safe-sex programs. These alternative programs were camouflaged with such misleading names as “abstinence-plus,” “comprehensive sex ed,” and, most recently, “evidence-based programs.”

The problem these advocacy groups have is that parents overwhelmingly support the messages in abstinence education, and oppose those in “safe sex.” For example, abstinence teaches that teens should abstain from sex at least until they have finished high school. Over 90 percent of parents agree. By contrast, comprehensive sex-ed programs teach that it is okay for teens to have sex as long as they use a condom. Only 9 percent of parents agree.

Abstinence curricula teach that sex should be linked to “love, intimacy, and commitment” and that these qualities are most likely to be found in marriage. Again, 90 percent of parents agree. But the sex-ed lobby is appalled at “privileging” marriage over casual relationships, cohabitation, or “hooking up.”

The contrast between the two approaches grows out of a fundamental difference of philosophy. When I speak to parents about sex ed, I often ask: “Suppose we invented a pill that offered 100 percent protection against pregnancy and all STDs. Would you then be happy to see your 16-year-old sexually active or to have your kid at college hooking up with random partners?” Nearly all parents answer no, but many have difficulty articulating why.

A good abstinence program explains why. Abstinence teaches that human sexuality is predominantly psychological, emotional, and moral rather than physical. While physical pleasure from sex is very important, it’s not an end in itself. The proper function of this pleasure is to strengthen a long-term bond of love and commitment. Sex that does not promote long-term emotional bonding is to be avoided.

This old-fashioned perspective is validated in the oddest place: Hollywood. In films, sex usually happens, steamily, between attractive unmarried couples who have just met. But at the end, the loving couple heads off together, in a vague but presumably long-lasting union. A film that ended with the protagonists cavalierly going their separate ways would offend or disappoint most of the audience. This script-writing habit shows that the human mind (even if only subconsciously) regards casual sex as unrewarding, and believes that sex should, optimally, lead to love and bonding. It is this commonsense view, implicitly embraced by nearly all adults, that abstinence education strives to reinforce.

Not so comprehensive sex ed. These curricula read as if they were written jointly by Hugh Hefner and a school nurse. Sex is all about transitory physical pleasure: The goal is to attain it while avoiding serious disease and unwanted pregnancy. They offer a present-oriented view of sex without commitment, entanglement, or consequence — a world designed for 17-year-old males.

Their main message: Hook up, have fun, but wear that condom. Condom rhapsody is pervasive, with teachers telling students to “eroticize condom use with partner . . . use condoms as a method of foreplay . . . act sexy/sensual when putting the condom on . . . hide them on your body and ask your partner to find it . . . wrap them as a present and give them to your partner before a romantic dinner.”

Aware that not all parents will be thrilled with programs that teach students to “tease each other manually while putting on the condom,” comprehensive-sex-ed writers usually “balance” their permissive texts with token statements about abstinence. They may comment briefly that “abstinence is the safest choice.” Since the text has just spent 50 pages explaining that sex with condoms is fun and really safe, however, such comments simply make abstinence seem pointless. Students are never given a reason to abstain. No surprise, since comprehensive-sex-ed experts believe no such reason exists: In their world, protected teen sex has no downside.

A final difference between the competing sex-ed models involves the collapse of marriage in lower-income communities. Federal abstinence funding began as part of welfare reform in the mid-1990s with the goal of slowing the growth of illegitimacy. Nearly 40 percent of American children are born outside marriage, most of them to less-educated women who will have a tough time going it alone. In many lower-income communities, the rate reaches 80 percent. The decline of marriage and the growth of single parenthood are the predominant causes of child poverty in the U.S. The cost to taxpayers is some $300 billion in welfare each year. In low-income neighborhoods, abstinence programs were designed to be a small first step in confronting this disaster.

To comprehensive sex ed, on the other hand, the collapse of marriage is irrelevant. True, these programs talk about “teen pregnancy,” but only about 7 percent of non-marital pregnancies happen to girls under 18. About the vastly larger problem of non-marital pregnancy and births among young adults, sex ed is conspicuously silent.

Moreover, the Left’s omnipresent solution (ever more condoms) is irrelevant to the real cause of non-marital pregnancy among low-income adults and teens. Harvard sociologist Kathryn Edin recently studied non-marital pregnancies among low-income girls and women and found that none were caused by lack of access to birth control. Rather, the pregnancies were deliberate, or at least not specifically avoided.

Abstinence education seeks to address the complex motivations underlying non-marital pregnancies and births. It attempts to deter them by explaining the value of marriage to adults and, especially, to children. But teaching low-income youth about the benefits of marriage treads heavily on the bunions of political correctness. To the Left, the pro-marriage information in abstinence programs is a compelling reason to eject them from the schools.

Thus President Obama and Speaker Pelosi have abolished federal abstinence programs and provided new funding for comprehensive sex ed. A thick smoke screen still blankets the issue. Congressional liberals would like everyone to believe that sex-ed programs share the same goals; the only question is which program is most effective — as it were, which makes the trains run on time. But the real issue is not the trains’ timeliness, but where the trains are going. Abstinence and comprehensive sex ed proceed from opposing values — and are bound for very different destinations.