Two weeks ago, Timken High School of Canton, Ohio made national headlines with the revelation that fully 13 percent of its female students were pregnant in 2005. The school offered only abstinence-based sex ed courses, and Columnist Dan Savage summed up the prevailing liberal sentiment in four words: "Good Work, American Taliban!"

But the 64 pregnancies were less interesting than the school's board's implicit acceptance of blame. The board decided that Canton schools would adopt sex-ed curriculums that promote contraception. That pregnancy rates were a function of a high school curriculum went unquestioned. Adolescent sex, apparently, indicates a policy failure, and public school parents have a grand total of two policy options: the comprehensive sex ed preferred by the left, or the abstinence-only version preferred by the right. Having the government teach coitus along with math and science has become so ingrained that the old conservative response to teaching sex in the classroom—don't—has dropped out of the conversation.

It wasn't always this way, as sociologist Kristin Luker explains in her new book, When Sex Goes to School, a study of America's tortured sex ed debate. Luker, a professor at the University if California, Berkley, has studied the evolution of sex ed for 20 years, following four American communities as the controversy developed. She stays remarkably objective about the whole business, but the story that emerges is that of a liberal policy hijacked to serve conservative ends. It's a fascinating look at big government conservatism ascendant.

Between the early '70s and '80s, Luker reminds us, teaching contraception was relatively uncontroversial. A few groups were opposed, but the issue of whether Sally should spend class time fitting condoms over fruit just wasn't the stuff political platforms were built on. "Yet opposition to sex education," writes Luker, "once the purview of what was called the "radical right" moved in just a little over a decade to the center of the Republican Party."

How did this happen? In a word, funding. As groups like Focus on the Family and Conservative Women for American coalesced around pro-family policies in the late 70's, sexual ed proved a proxy issue for much of what they mourned in contemporary America: the decline of the family, the coarsening of the culture, the glorification of sexuality. In 1981, two Republican Senators, Orrin Hatch (R-Utah) and Jeremiah Denton (R-Ala.), introduced the Adolescent Family Life Act (AFLA). Its straightforward purpose was to divert funds from liberal educators to traditionally minded groups who would provide alternatives.

Conservatives now had a cut of the sex-ed slush fund, but it doesn't cost money to talk to kids about sex at home. Parents who were offended by their kids' curriculums in the late 70's had nothing to offer. But AFLA money funded the prototype abstinence-only program, which became a boxed and ready-to-go response to contraceptive promotion. To counter the "mixed messages" paraded by liberals, conservatives would offer one sober refrain: Don't do it. Whereas conservatives had little to say to parents who warned that uninformed kids would die of AIDS, conservatives could now impart the unassailable truth that nothing is safer than abstinence. And whereas liberals had happily imposed their condom-happy values on the sons and daughters of conservative parents, conservatives could stand before the sons and daughters of liberal intellectuals and preach the wonders of waiting.

As so often happens, the "moderate" position—teaching sex ed without mention of contraception—was by far the most moronic. Teaching abstinence cost money and class time but conveyed little information. Government employees working out of publicly available educational materials told students sitting next to 30 of their peers that sex was essentially a private matter. How's that for a mixed message?

But the lessons themselves were never the point, as becomes clear in Luker's interviews with parents on both sides. The emotional intensity involved suggests much larger questions of gender and marriage, hierarchy and equality. Her interviewees cannot stick to the subject, digressing into disgust for "the '60s" and "the gay lifestyle," disdain for Christians, aversion to early marriage, shifting gender roles, and virtually any other social issue imaginable. One mother says she supports abstinence-only education because her husband raped her daughter. That's the kind of rage being channeled into vitriolic arguments over whether 300 9-year-olds should be told that it's OK to masturbate. The rhetoric is insanely disproportionate to the significance of what is being argued.

Perhaps that's why no one seems to care that sex education of any stripe may be ultimately pointless. At the end of a 259-page book on the subject, Luker can't find a single study robust enough to back. She sighs, "We are looking for an outcome, teenage sexual behavior, that is affected by many forces, only one of which is sex education, during a period of tremendous social change, which has surely had some independent impact on such behavior, and we are looking at everything from one class room period to a semester's worth of classes, all in the service of trying to see if they affected the outcome."

Sexual behavior is too overdetermined, self reports too unreliable. Luker's survey of Europe suggests that any claims for the efficacy of sex ed are tenuous at best. In Sweden, sexual education is far more intensive and comprehensive than in the U.S. In France, programs are less common than they are stateside. Yet Sweden and France have similar rates of sexually transmitted disease and teen pregnancy. Both are far lower than those in the United States.

In short, sex education of any stripe turns out to be faith-based, premised as it is on the assumption that sex education and sexual behavior are tightly linked. Luker ignores her professed lack of confidence in sex education and offers a non-solution: Teach the controversy. But why, if it is likely a waste of time, entertain the controversy at all? The question isn't even addressed. Parents are locked in an educational arms race, and neither side is going to give first.

That Americans can look at 64 pregnant teenagers in Ohio and immediately stake positions in the culture war suggests the debate has less to do with troubled teens than with adult politics. And that is the most striking thing about Luker's 20-year study: The deeper you delve into controversies over the sexual education of public school kids, the easier it is to forget kids were ever involved.