In Namibia, some teachers would hide when it was time to lead the sex-ed class. In South Africa, they would write "HIV" on the blackboard and have students mouth back what it stood for. In Nepal, one teacher tasked with sexual education was dubbed "Reproductive Sir," light fare compared to what female instructors in Kenya, Nigeria and Thailand have been called by their communities: vulgar, promiscuous and prostitutes.

Clearly, sex ed is a headache for many families beyond Ontario, where parents recently stared down Premier Kathleen Wynne's controversial new curriculum. To be implemented this fall in elementary and high schools, the modernized lessons proved divisive among moms and dads who believe sex ed should "happen at home," and those clamouring for up-to-date information doled out in school.

It's a conflict that recurs around the world, says New York University professor of education and history Jonathan Zimmerman. His new book Too Hot to Handle: A Global History of Sex Ed, a comprehensive international chronicle of sex education, traces the challenges in the developing world, as well as newer obstacles: globalization and the Internet.

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"School probably isn't very well equipped to challenge the power, immediacy and volume of all the things students see on screens," Zimmerman says, pointing to the ubiquity of online porn. On top of that, he argues that teachers woefully lack pedagogical skills and parental support – two things teachers absolutely need if they're ever to deliver the kinds of ambitious and interactive sex-ed classes officials are envisioning.

Sex ed is now doubly contentious thanks to globalization, which has added objectors even in places often assumed to be liberal on the subject, such as Sweden. In diverse immigrant hubs, sex ed moves from being a health issue to a political hot potato: Whose morals should children subscribe to – health authorities' or their own community's?

"We have homegrown conservatives joining hands with this much larger and much newer population, with whom they agree about almost nothing except for sex ed," Zimmerman says. "The more democratic we become, the more problematic sex ed is going to be."

So if sexual education is perpetually playing catch-up with tech, whistle-toting phys-ed coaches remain painfully ill-equipped to deliver lessons on the front lines, and parents increasingly disagree about what their kids should and shouldn't know, why are we even still trying to tackle sex through school?

"I think we have to try," Zimmerman says. "Schools' job is to try to raise citizens. Especially in this media environment where some people are getting really twisted and violent ideas about sex, schools should try as best they can to address this. But they have to proceed really gingerly."

Here, a glance at how it's done outside Canada:

Scandinavia

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Considered a model of sexual-health education, Sweden was a forerunner, mandating lessons since the 1950s. For decades, sex ed in Scandinavia has been less about scare tactics and more about "sexual self-determination," Zimmerman explains. "The goal wasn't defensive, like it so often is in North America and in the U.K. It was much more oriented toward helping the individual develop a sexual life." Teaching sexual agency often means being more explicit. Zimmerman describes a Swedish teacher passing out condoms and urging students to experiment at home: Boys were instructed to masturbate with various types to see which they preferred and girls were told to practise opening the package. Earlier this year, a Swedish public broadcaster screened an educational cartoon featuring dancing penises and vaginas during a children's program (sample lyrics: "The vagina is cool, you better believe it, even on an old lady. It just sits there so elegantly"). In Finland, government authorities send condoms and sex-ed leaflets to all teens on their 16th birthday.

France

Despite its libertine image (and progressive stance on sexual and reproductive rights), Zimmerman argues that France has historically tried to sidestep sex ed because it's so intimately related to values and religion. The author traces the roots of this attitude to France's tradition of secularism: "Schools were supposed to just teach the facts. When the sexual revolution came along and some teachers started to teach about sex ed, what the French said was you can teach plumbing – what goes where, sperm meets egg – but you can't get into discussions of the subject because that will involve values," he said. Earlier this month, the secretary of women's rights blasted French public schools for not teaching sex ed comprehensively or "equally," specifically around young women's reproductive choices. That said, the government launched lessons about combatting gender stereotypes in its schools in 2013.

Britain

The British government announced earlier this month that children would be taught about consent starting at age 11, the idea being to get them learning about consensual relationships before they are sexually active. But critics argue that until sexual education becomes mandatory in the U.K. – currently it is not – the message will be lost. Parents are allowed to exempt their children from sex ed – "the right of withdrawal" has existed since 1996. Even with the opt-out clause, some religious parents here "feel that the presence of what they feel is this godless and even immoral point of view … is going to seep into other parts of the curriculum," says Zimmerman. "Opting out becomes a more complicated matter when it's woven into other parts of the curriculum."

Poland

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Post-communism, Catholics revoked compulsory (and also highly rudimentary) sex ed in 1993. Later, when it was reinstated as an anti-abortion measure, sex ed was taught by priests in the country. Intended to delay sex and promote marital fidelity under the banner of "Family Life Education," parental consent was required. "It's been very much a football, politically," says Zimmerman. "After the fall of communism, people became more free to promote sex ed. And they also became more free to oppose it."

United States

Three types of sex-ed curriculums appear throughout the United States: comprehensive (medically accurate information), abstinence-based (mostly abstinence, some science) and abstinence-only. The Obama administration has scaled back federal funding for abstinence-only education, which has been heavily subsidized since the Reagan era despite evidence that it's ineffective at preventing sexually transmitted infections. But with just 22 states and Washington, D.C., legally requiring sex ed be taught in public schools, the country is only beginning to discuss healthy relationships and safe sex in tandem with waiting till marriage. With no standard, Zimmerman notes that there's enormous variation across the country's 14,000 school districts: "Sex ed in Lubbock, Texas, will inevitably look different from sex ed in Brooklyn, New York."

Africa

Sex education in Africa has largely focused on combatting the AIDS epidemic. To raise visibility, Botswana incorporated sex ed and HIV awareness materials into science, home economics and religious education; Kenya did the same through its geography, history, civics, Swahili and math classes. Still, teachers trying to convey sexual education face immense obstacles: "There's an incredible amount of anxiety and disagreement about the entire question of youth sexuality," Zimmerman says. "And teachers often have tenuous cultural and professional authority. You put those two things together and sex ed becomes massively problematic."

Japan

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American occupying forces introduced "family life education" in the late forties; "Purity Education" was the Japanese name for it. The curriculum acknowledged sexuality as healthy, provided it existed within marital unions. That conservative bent continued through to the height of the AIDS crisis, when Japanese health officials falsely denied the country had a problem with the disease. School textbooks eventually acknowledged AIDS but in an extremely limited way, debunking myths about AIDS spreading via toilet seats, mosquito bites and shaking hands, but failing to accurately explain how AIDS is actually transmitted. Today, Japanese sex ed tackles human development, pregnancy, family values and healthy gender concepts. There are signs of change: a poster explaining diverse sexual orientations and reportedly hung outside a school nurse's office in Japan went viral last year. Titled "Who Will You Come to Like?" the poster read: "Sexual orientation is innate and it cannot be changed by intervention, so there is no need to change your preferences."

Iran

Surprisingly, some of the most sexually explicit instruction occurs in Iran, Zimmerman found. Here, curricula emphasize "the consent and readiness of the woman" and "the enjoyment of each partner." The catch, Zimmerman says, is that Iranian authorities only promote sex within (heterosexual) marriage. A blessing from God, "Sex is a healthy thing, sex is a vital thing, sex is a good thing, provided it's within the marital union," Zimmerman says. "The added Koranic twist is that this is a duty of the husband and the wife to each other."

China

The focal point in school remains academic success, with few institutions offering any sex ed at all. Zimmerman writes about health officials doing some "corrective sex education" to stem the tide of online pornography. Sex ed here is viewed as a "fire extinguisher" against the flames of Western "sexual liberation," although many Chinese parents see the two as one and the same problem.People have taken to posting brief explanatory sex-ed videos on Youku, the Chinese version of YouTube, to help each other out. The animated shorts, one of which compares genitalia to electrical outlets and plugs, quickly went viral.