In 1976, the British psychologist Rex Stanton Rogers replied to an angry letter from T. J. Proom, who had withdrawn his four daughters from their public school in the south east of England to protest its allegedly “pornographic” sex education lessons. The editor of a recent collection of essays on sex education, Rogers made it clear that he did not share Proom’s views on the subject. At the same time, though, Rogers was sympathetic to his plight. “There are arguments both ways about the distribution of power and about parental rights in education,” Rogers wrote. “In the specific area of sex education schools vary vastly in policy both over the topic and the role of parents—again I’d hate to say what ought to happen.” On other controversial educational questions, Rogers noted, the “conventional answer” was to expose children to a “plurality of opinion” so that they could form their own. But adults were reluctant to do that on matters of sex, Rogers told Proom, because the stakes were so high:

A lot of sex educators have a “health” orientation. They sex educate for the same reasons that others tell us to wear seatbelts, give up smoking or get our children vaccinated/immunized. In the process a few people die in car fires, survive to 90 smoking like chimneys, or get brain damage from vaccines. But many more forms of suffering are avoided—or so the argument goes. You are among the “unlucky” in this argument. Your children may have been “saved” from unwanted pregnancies, sexual “guilt,” etc. There isn’t much direct evidence that this is true, in the end sex educators are working on hypotheses. If they are wrong they will get hammered like the planners that put people into high-rise, if they are right they will be hailed as new Pasteurs.

Rogers’s remarks neatly encapsulated both the broad ambitions and the dashed hopes of sex education in the modern world. From the dawn of the twentieth century, advocates imagined that schools could transform the sexual lives of young people. Some of these visions focused on changing their behavior, to minimize “unwanted pregnancies” and especially sexually transmitted diseases; others emphasized changing their minds, so they could be liberated from “guilt” and other unhealthy ideas. But sex educators were stymied at every turn by dissident parents and communities, who wanted schools to teach their ideas about sex—or nothing at all. “We are not against sex education—quite the reverse—but we do not want modesty, chastity, and fidelity to be undermined in our child,” T. J. Proom wrote, in a revealing follow-up letter to Rex Rogers. Nor did he want schools to present a wide array of “opinions” on the subject, as Rogers had suggested. “How do those who believe in reticence counteract the effect of those who impose pornography on children?” Proom asked. “Surely to subject children to a Babel of dissonant voices is to invite cynicism and a myriad of excuses for selfindulgence.” As he correctly sensed, even a curriculum oriented toward sexual autonomy and decision making expressed a set of values, about sex and reason and—most of all—about individuality. Whether sex education spawned sexual “self-indulgence” or not, there was no mistaking its focus on the self.

That emphasis echoed the proclaimed values of state-run schools, of course: order, rationality, and individuality. In the twentieth century, for the first time in human history, schools became truly universal institutions; most of the world’s people entered their doors, for at least a part of their lives. And wherever they appeared, schools ostensibly taught people to view themselves as rational and purposeful actors who can make their own choices and construct their own lives. More often than not, as many chroniclers have noted, the day-to-day demands and constraints of schools inhibited or squashed this individualist ideal. But as the history of sex education reminds us, the ideal is hardly shared; instead, it is one of the most hotly contested questions of modernity. Examine almost any sex education document—in almost any part of the globe—and you will find statements exalting the conscience and choice of the rational individual, just as you do in the rest of the curriculum. Sex is a highly personal matter, the story goes, so schools should equip each person with the skills and knowledge to navigate its perilous shores. To many people around the world, however, that idea offends their conscience; they want schools to map proper sexual behavior, not to liberate individuals to explore it on their own. “The scheme took what it called ‘reason’ as the basis for morality,” a British conservative wrote in 1972, condemning a new sex education project. “What is called didactic teaching about right and wrong was to be abandoned in favour of the child’s ‘self-evolved solutions.’” The writer’s use of quotation marks punctuated his own skepticism. When it came to sex, many adults believed, there was no good reason to let children come to their own reasoned conclusions.

Nor did they believe that expert authority should trump their own, a central theme of campaigns against sex education—and, more largely, of political conservatism—in the modern West. Since the 1970s, sex educators have linked their opponents to antievolutionists and (more recently) to climate-change deniers; in each case, the argument goes, the right wing mobilized its populist legions to counter established scientific truth. But sex education simply lacks the scientific basis or consensus that marks topics like evolution and human-made climate change. To be clear, no credible research has ever sustained the conservative claim that sex education makes young people more likely to engage in sex. Yet there is also scant evidence to suggest that it affects teen pregnancy or venereal disease rates, either, as pioneering American sex researcher William H. Masters acknowledged in a 1968 interview with Playboy magazine. “We have no scientific knowledge as to whether it’s worth a damn,” admitted Masters, whose studies (with Virginia Johnson) of “human sexual response” made them both household names. “There are a lot of people who climb on the sex education bandwagon and say it’s great. But somebody is going to take the time and effort to find out whether there is any real value in the entire concept of formally disseminating sexual information to youngsters.” Since then, scholars around the world have struggled in vain to show any significant influence of sex education upon youth sexual behavior. As a British scholar observed in 2009, the three European countries with the lowest teen pregnancy rates—Italy, Switzerland, and the Netherlands—all took very different tacks on sex education. Italy’s approach was particularly “haphazard,” the scholar noted: sex education provision was “sparse,” parents retained the right to withdraw their children from it, and one survey showed that half of eleven to fourteen-year-olds believed they could acquire AIDS from a toilet seat. Yet the incidence of teen pregnancy was about the same as in Holland, where youth received much more extensive sexual instruction at school.

Given how sporadically most countries taught sex education, we should not be surprised by the lack of strong data about its behavioral effects. Nor was it clear whether the subject altered individual attitudes, another avowed goal of some—not all—sex educators. This ambition sat uneasily next to educators’ repeated claim that they merely sought to disseminate “science” or knowledge, not to change children’s minds. But they inevitably taught values, too, whether they admitted it or not. “Most forms of education (like teaching French rather than Cantonese) involve value judgments about what is useful to the child, good for society, and so on,” Rex Rogers noted in his letter to T. J. Proom. “Even an apparently neutral subject like mathematics has this characteristic.” There was nothing even nominally neutral about sex education, of course, which addressed one of the most intimate dimensions of the human experience. Some educators stressed changed values as a route to improved behavior, insisting that youth would never become sexually continent or responsible until they altered their confused and repressed attitudes about sex. To others, however, fighting repression was an end in itself. “I want these children to learn to experience pleasure without feeling guilty,” declared the radical Brazilian educator Paulo Freire, praising a São Paulo pilot project in sex education in the 1980s. “School has to sweep away taboos and sexual prejudices because sex is one of the most important sources of pleasure known to human beings.”

But many human beings did not see it that way, in Brazil or around the world. For some, the goal of individual freedom insulted religious or communal prescriptions about sex and sexuality; to others, it violated their own individual rights to raise children as they saw fit. Over the past three decades, as a host of scholars have documented, human rights have become a kind of lingua franca for the modern world. Sex education supporters frequently employed human-rights language, insisting that children’s rights—as codified in a growing series of international treaties and conventions—guaranteed the right to receive sexual knowledge and information. But opponents invoked the rights of parents, especially as encoded in what Michael Ignatieff has called the “sacred text” of the twentieth century: the 1945 Universal Declaration of Human Rights. “Parents have a prior right to choose the kind of education that shall be given to their children,” the declaration states. It also calls the family “the natural and fundamental group of society,” entitled to “protection by society and the State.” As the 1976 Kjeldsen case in Europe illustrated, conservative efforts to harness human rights principles against sex education sometimes fell short of their mark. But they also spoke to the “globalization of the ‘family values’ movement,” as an Australian observer noted in 2007. The first “family values” campaign came out of the American New Right, of course. But it had become thoroughly internationalized, drawing on worldwide networks—and, increasingly, on worldwide human rights doctrines—to mount a global attack on sex education.

When it came to sex, however, the most influential global force was never the school. Starting with magazines and films and culminating in television and the Internet, mass media had a much more profound effect on children’s sexuality in the twentieth century than any set of formal educational institutions. Indeed, sex educators often designed their curricula as an explicit challenge to crass media images and ideologies. To an American educator, writing in 1914, “youth is subjected by our civilization [to] aggressive sex stimuli and suggestiveness oozing from every pore”; a French physician worried in 1959 that “theater, film, pornographic publications and posters ... cause a state of sexual over-excitement,” which he compared to “a poisoning gas”; and in 1971, a Japanese educator warned that her country was “flooded” with obscenity and pornography from overseas. “Much of what is produced in the mass media today is ‘Sexy’ in the extreme,” she complained. “How best can it be counteracted?” The question became even more urgent in the era of the Internet, when millions of sexual images could be accessed with a few clicks of a mouse. In China, the popularity of Japanese porn stars—and the weakness of the Chinese “Great Firewall,” which technology-savvy adolescents could scale with ease—prompted officials to insert sex education for the first time into the national health curriculum. As a New Zealand journalist surmised, after observing several sex education classes in 2006, “schools are being forced to play catch-up with popular culture.”

Could schools ever “catch up”? History suggested the opposite: try as they might, schools would always be a step—or three—behind the sexual curve. “A 12-minute filmstrip is hardly a match for two years of ‘R’-rated films every weekend,” wrote Scott Thomson, director of an American principals’ association, in a bold 1981 article. “A few chapters of a textbook on marriage and family cannot really compete with Hustler, Oui and Playgirl and Masters and Johnson. The school marching band plays ‘Stars and Stripes Forever’ but the students listen to ‘Afternoon Delight’ on their cassettes.” Indeed, Thomson continued, “schools are a puny David without even a sling-shot against the media Goliath.” But they pretended that they could slay the giant, nevertheless, perpetuating a kind of “educational fraud” on the entire nation. “As long as one set of values is taught in the larger society, it is absurd to ask schools to neutralize those values in a few weeks of classroom instruction,” Thomson concluded. “Even more absurd, however, is the expectation that any significant outcomes will come from that instruction.” He was probably right. Even in Sweden, as a 1969 observer wrote, sex education “tended to follow rather than lead social trends”; two decades later, Sweden’s leading sex educator agreed. “Sex education will not be really accepted before a profound change of attitudes in broad groups of the society has occurred,” wrote Carl Gustaf Boethius, the longtime head of the Swedish Association for Sexuality Education, summarizing a set of reports about the subject in different European countries. “Things must happen first in society and only then in schools.... The school is not a spear head, it is a mirror.”

That is not to say that schools have failed entirely in this realm. Surely, across the twentieth century, many teachers and schools have helped children gain more insight, understanding, and knowledge about their sexual lives and selves. When he taught high school social studies in Colorado in the 1930s, for example, the future bestselling author James A. Michener designed and cotaught a pilot sex education class with a science instructor. Boldly mixing boys and girls in the same classroom, the freewheeling course covered such controversial subjects as birth control and masturbation. Students raved about the class, and—most notably—not a single parent complained. “The bogey-man of parental interference . . . is grossly overexaggerated,” Michener wrote. “We believe that most American communities will eventually react in this same way if sane teachers teach those fields.” He was wrong, obviously, about America and the rest of the world. Over the past hundred years, there is probably no subject that has posed greater headaches to teachers than sex education. However “sane,” to borrow Michener’s dated metaphor, some teachers obviously lacked the skills and preparation to teach the subject; others were hampered by community pressures from every side, which accelerated—not abated—after Michener’s time. But they were most of all stymied by sex itself, which resisted most efforts to rationalize and systematize it in the modern school. “To the theoretical teacher eager to reform the world on paper the introduction of sexual education into the curriculum of our schools may appear a very simple step,” a British author and former headmistress wrote in 1920. “Are we really being honest with ourselves? For in sex we have yet learnt very little, and this is true even of the wisest among us; and indeed, I doubt sometimes if we can ever learn very much except each one of us for ourselves out of our own experience.”

“Experience” was a hallmark of twentieth-century educational reform movements around the world, which sought to make schools more “practical” and relevant to students’ day-to-day lives. Sex educators seized eagerly on this idiom: like health and vocational classes, the argument went, instruction about sex would prepare young people for real-world activities and decisions. “In this day of progressive education,” an American school official wrote in 1939, “when schools teach children ... habits of healthful living; what foods they should eat; how to use carpenters’ tools; how to cook, sew, manage a household, dress, and prepare themselves to earn a living, it is hard to believe that our boys and girls are still left to acquire sex instruction in the gutter.” He should not have been surprised. For millions of people around the world, the so-called 3 R’s—reading, writing, and arithmetic—remained the sine qua non of proper education; “practical” or “experiential” learning was second rate or superfluous, best obtained outside of schools rather than within them. It also seemed especially pernicious in the realm of sex, where it conjured precisely the behaviors that most adults wanted to prevent. “Modern educational experts believe in ‘learning by doing,’” an American conservative wrote in 1970, “and we all know what explorations can take place ... stimulated by film strips and class discussions about sex.” That same year, but an ocean away, a British critic issued a nearly identical warning. “Children are always eager to put their knowledge into practice,” he wrote. “Where would their experimentation end?” Rooted in the modern doctrine of learning via experience, sex education alienated parents and other citizens who did not want students to experience sex.

For the world’s children, for the past hundred years, most of this experience has taken place far from the classroom. The rise of near universal education in the late twentieth century made schools into sexual spaces; indeed, sex education was often designed to purify their erotic atmosphere. But children learned much more about sex from their peers—and from mass media—than they did from teachers, parents, or any other authority figures. In a much-told joke from Mexico, a father informs his son that they need to have a “frank, heart-to-heart talk” about sex. “OK, Dad, what is it you want to know?” the son replies. The joke was on adults, of course, who like to pretend that their children are sexual innocents. But so do schools, which have never influenced sexual knowledge or behavior to the extent that they wanted, or believed. In Sweden, another popular joke described an eight-year-old boy whose teacher announces that his class is about to receive its first sex education lesson. “Miss, couldn’t we who already know how to fuck be allowed to go out to play football?” the boy asks. For the most part, on matters of sex, schools “taught” the world’s students what they already knew. Sex education was neither a modernist monstrosity like high-rise public housing nor a “new Pasteur” of scientific triumph, to quote Rex Rogers. It was instead a mirror, reflecting all the flux and diversity—and the confusion and instability—of sex and youth in our globalized world.

Excepted from Too Hot to Handle: A Global History of Sex Education by Jonathan Zimmerman. Copyright © 2015 by Princeton University Press. Reprinted by permission.