Until last winter, I had assumed that fundamentalist feminism had peaked in the early 1990s with the Anita Hill brouhaha, and that Bill Clinton’s political survival in 1998, which hinged on his near-unanimous support from hypocritical feminists, ended the era in which anyone took feminism seriously.

The Larry Summers fiasco, however, showed that while feminism may have entered its Brezhnev Era intellectually, it still commands the institutional equivalent of Brezhnev’s thousands of tanks and nuclear missiles. After just a few days, Harvard President Lawrence Summers caved in to critics of his off-hand comment that nature, not invidious discriminations alone, might be to blame for the lower percentage of women who study math and science. In short order, he propitiated the feminists by promising, in effect, to spend $50 million taking teaching and research opportunities at Harvard away from male jobseekers and giving them to less talented women.

Perhaps in a saner society, then, we would have less need for Leonard Sax’s engaging combination of popular science exposition and advice guidebook, Why Gender Matters: What Parents and Teachers Need to Know about the Emerging Science of Sex Differences. But parents as well as professors could benefit from it now.

Sax speaks of “gender” when he means “sex”—male or female. I fear, though, that this usage battle is lost because the English language really does need two different words to distinguish between the fact, and the act, of sex. Supreme Court Justice Ruth Bader Ginsburg claims her secretary Millicent invented the use of “gender” to mean “sex” in the early 1970s while typing the crusading feminist’s briefs against sex discrimination. Millicent pointed out to her boss that judges, like all men, have dirty minds when it comes to the word “sex,” so she should use the boring term “gender” to keep those animals thinking only about the law.

Unfortunately, “gender” now comes with a vast superstructure of 99% fact-free feminist theorizing about how sex differences are all just socially constructed. According to this orthodoxy, it’s insensitive to doubt a burly transvestite truck driver demanding a government-subsidized sex change when he says he feels like a little girl inside. Yet it’s also insensitive to assume that the average little girl feels like a little girl inside.

Fortunately, Sax, a family physician and child psychologist, subscribes to none of the usual cant. Indeed, I thought I was a connoisseur of sex differences until I read Why Gender Matters, where I learned in the first chapter, for instance, that girls on average hear better than boys, especially higher-pitched sounds, such as the typical schoolteacher’s voice, which is one little-known reason girls on average pay more attention in class.

Males and females also tend to have different kinds of eyeballs, with boys better at tracking movement and girls better at distinguishing subtle shades of colors. Presumably, these separate skills evolved when men were hunters trying to spear fleeing game and women were gatherers searching out the ripest fruit. So, today, boys want to catch fly balls and girls want to discuss whether to buy the azure or periwinkle skirt. Cognitive differences are profound and pervasive. Don’t force boys to explain their feelings in great detail, Sax advises. Their brains aren’t wired to make that as enjoyable a pastime as it is for girls.

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As founder of the national association for Single-Sex Public Education, Sax’s favorite and perhaps most valuable theory is that co-educational schooling is frequently a mistake. He makes a strong case, especially concerning the years immediately following puberty. He cites the experience of two psychologists studying self-esteem in girls. They went to Belfast, where children can be assigned fairly randomly to coed or single-sex schools:

They found that at coed schools, you don’t need to ask a dozen questions to predict the girl’s self-esteem. You have to ask only one question: “Do you think you’re pretty?”

Similarly, the Coleman Report found, four decades ago, that boys put more emphasis on sports and social success in coed schools, and less on intellectual development. Sax argues:

Here’s the paradox: coed schools tend to reinforce gender stereotypes. There is now very strong evidence that girls are more likely to take courses such as computer science and physics in girls-only schools. Boys in single-sex schools are more than twice as likely to study art, music, foreign languages, and literature as boys of equal ability attending comparable coed schools.

Noting that the Department of Education projects that by 2011 there will be 140 women college graduates for every 100 men, he asks, “I’m all in favor of women’s colleges, but why are nominally coed schools looking more and more like all-women’s colleges?”

So far, the decline of male academic achievement in the U.S. is mostly among blacks and Hispanics, but the catastrophic downturn into “laddism” of young white males in England in recent years, and their consequent decline in test scores, shows that no race is permanently immune to the prejudice that school is for girls.

Of course, American schools have long been taught largely by women, and boys and schoolmarms have not always seen eye-to-eye. But the rise of feminism has encouraged female teachers to view their male students as overprivileged potential oppressors. Further, feminism justifies teachers’ self-absorption with female feelings. Thus, a remarkable fraction of the novels my older son has been assigned to read in high school are about girls getting raped. I hope it hasn’t permanently soured him on fiction.

We’ve now achieved the worst of both worlds: the educational authorities are committed to anti-male social constructionist ideology, but the pop culture market delivers the crudest, most sexualized imagery. The irony is that when the adult world imposes gender egalitarianism on young people in the name of progressive ideologies, it just makes the young people even more cognizant of their primordial differences.

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Sax’s book often resembles a nonfiction version of Tom Wolfe’s impressive novel I am Charlotte Simmons. What’s most striking about Wolfe’s merely semi-satirical portrait of Duke University is how, after 35 years of institutionalized feminism, student sexuality hasn’t evolved into an egalitarian utopia. Instead, it has regressed to something that a caveman would understand—a sexual marketplace where muscles are the measure of the man.

Not all of Sax’s arguments are so dependable. For instance, he is far more confident that homosexuality is substantially genetic in origin than is the leading researcher he cites in support of his assertion, J. Michael Bailey of Northwestern University. Bailey has publicly noted how challenging he has found it to assemble a reliably representative sample of identical and fraternal twins for his homosexuality studies. Further, Bailey is troubled by the fundamental objection that natural selection would, presumably, cause genes for homosexuality to die out. Sax, though, races past these prudent concerns.

Still, this is a better than average advice book for mothers and fathers. Most parenting books are unrealistic because they overemphasize how much parents can mold their children’s personalities. Raising a second child, with his normally quite different personality, typically undermines parents’ belief in their omnipotence, but most child-rearing books hush this up because their market is gullible first-timers. Fortunately, by emphasizing how much you need to fine-tune your treatment to fit your child’s sex, Why Gender Matters injects some needed realism into the genre.

But Sax’s bulletproof confidence in his own advice gives me pause. Sixteen years of fatherhood have left me less confident that I know what I’m doing than when I started, but he doesn’t suffer from any such self-skepticism.