Are single sex schools suddenly cool? Thirty-five girls’ schools have been founded since 1995, several of them public. Two hundred forty public institutions in this country offer some form of single sex education, up from three ten years ago.

And there are soon to be more.

On November 24, the U.S. Department of Education implemented new rules interpreting Title IX, the landmark Civil Rights legislation of 1972. These rules will allow—and implicitly encourage—American public schools to be single sex.

More than 98 percent of schools in the U.S. are co-educational. Historically, the justification had more to do with economic sensibilities than educational philosophies. It was cheaper, and perhaps more efficient, to make schools for males and females together. Once people accepted the (once radical) notion that girls had brains, it was even egalitarian to educate the two sexes in the same classroom with the same teacher.

As it turns out, however, boys and girls do not have the same experience in school, no matter how integrated the sexes are. Research over the last decade or so, found mainly in reports from the American Association of University Women, contains a profusion of studies showing that girls fare poorly in co-ed schools: They are ignored, patronized, passed over; when teachers give girls personal attention, it is often about outfits and appearance; girls get good grades but poor scores on standardized tests; they have low self-esteem. Latina and African-American girls, in particular, are overlooked and underachieving. The classroom climate is “chilly” for female students, who are being “shortchanged.”

On the other hand, girls’ schools have created fertile learning spaces for their students. Girls from single sex institutions are more likely to study math and science, to study advanced placement subjects, and to study, period. Presumably they spend less time attending to grooming and garment selection. (According to one survey, girls at a single sex school estimated they saved 45 minutes a day when they began attending a single sex school and wearing uniforms.)

Girls and minority children of both sexes benefit from the academic climate, leadership opportunities, and role models found in single sex schools. Indeed, some recent research has showed improvement not only in academic subjects like math but also in attendance and behavior. Given that poor children of Hispanic and African-American minorities are most at-risk for dropping out, according to U.S. Department of Education’s 2002 report, this is a strong argument for single sex schools.

Caucasian boys in co-ed schools were thought to be doing pretty well: Teachers seem to favor boys, engaging them, correcting them, and guiding them. They are encouraged to be leaders, to dominate discussion, and to forge ahead intellectually.

But when researchers looked at boys closely, they saw that boys have lower reading and literacy rates than girls, and higher rates of suspension, expulsion, and dropping out. Researchers are now concerned that co-ed schools, especially at elementary grades, are neglecting boys’ needs, and not treating them fairly. Some educators and parents have cautiously suggested that single sex education might also make sense for boys.

Boys and girls, they pointed out, develop differently and are quite out of sync with each other. Most boys lag behind most girls developmentally. Although they perceive spatial relationships vividly and achieve large motor control early, their relationship to the physical world makes them less able to sit quietly, listen closely, and, in general, behave like girls.

For their part, girls typically use language more deftly, understand complex concepts sooner, and manifest small motor control at an earlier stage than boys. During reading circle at the library, they might sketch or color; the boys, meanwhile, might wrestle. In early grades, the school environment is conducive to the orderly, attentive female members of the class, not to the physically active male members.

Boys’ schools take into consideration normal male behavior and design the day around them. They can be counter-stereotypical, providing role models of men who mentor, who challenge, who inspire, sometimes by their evident affection for Cicero or the piccolo, for physics or Sandburg or ceramics. Manly examples of adults who have chosen without reluctance to teach and to pursue a passion that is not rich in monetary reward but, here at least, socially respected, gives children the opportunity to learn “there are many ways to be a boy,” as the Allen-Stevenson School in New York states in its mission statement.

But what about the argument that there are two sexes and they need exposure to each other? They do. They need to know how to treat each other fairly, generously, compassionately, but competing with their own gender for the attentions of the other doesn’t insure anything good.

In secondary school, relations between males and females are complicated by hormones. Adolescence is a famously difficult stage physically, socially, and emotionally, and, again, the different rhythms of the two sexes are not harmonious. In all, students’ agendas make concentrating a difficult task.

It is better that males and females meet to compete in debate or robotics and combine their abilities in theatre arts or community service. It’s more natural, less forced. “I have a boyfriend,” noted a smiling girls’ school senior. “I just don’t need to see him 24/7.”

What they do need—what our society needs for them—is a place where they explore concepts, behave kindly, and risk what one educator has called “the having of wonderful ideas.” Maybe in a single sex school.

Diana Meehan, Ph.D, co-founded the Archer School for Girls in Los Angeles in 1995. She is the author of “Learning Like a Girl: Educating Our Daughters in Schools of Their Own.”