The least convincing argument for government-run schooling is that it provides a 'social' experience for children.  Anyone who attended school has horror stories about the behavior kids learn from the social environment at schools and, if you are a parent with a school age child, you might even worry about it more than be relieved.

Single-sex schools would seem to relieve some of that pressure, just like some women or some men feel better at a single-sex exercise facility. Advocates of single-sex schools contend that there may be brain differences between girls and boys that benefit from different teaching styles, though neuroscientists have found no brain differences linked to different learning styles.

Instead, single-sex schooling is a negative, claim a group of psychologists, though their logic seems to be reaching a bit.  They contend that when sex segregation occurs, the students are left to infer reasons for the separation. Are boys not as good in some subjects? Are girls unable to learn in cooperative settings?  

They dismiss numerous studies showing a pedagogical benefit, claiming little evidence to support claims that single-sex schools are a better learning environment. "Our examination of the existing studies leads us to conclude that there is not scientific evidence for positive effects of single-sex schooling," said psychology Prof. Lynn S. Liben of Penn State."That's not to say that academic outcomes are definitively worse, but neither are they definitively better. Advantages have not been demonstrated."

Then they cite a few weeks watching pre-schoolers as demonstration of their claim. They watched preschool classes to look at effects of gender divisions among the students and found that after two weeks of teachers using gendered language and divisions, like lining children up by gender or asking boys and girls to post work on separate bulletin boards, they were able to find an increase in gender-stereotyped attitudes toward each other and their choice of toys, and they played less with children of the other sex.

Well, in the history of schools, that same behavior ('boys are icky') has been noted millions of times, including in the overwhelming majority when classes are mixed.  

What to believe?  Some sociologists claim that women are unable to perform if they are not at least 50% of a class, they feel pressured by stereotype threat and the potential for gender bias, and so a 100% same-sex class would seem to unlock the potential for all females.  Since most sex-segregated schools are private schools, and require admissions testing before students enter, they are not teaching all students the way public schools must. In 2006, the 1972 Title IX law barring gender discrimination was interpreted to allow for single-sex classes if it led to better education.  

Education is certainly better, despite what detractors claim.  Standardized test scores, the very thing foreign schools specialize in and that are used to criticize the education of American children, have gone up every time since No Child Left Behind was instituted and for the first time female math scores are on par with males.

There is a minor effort to institute more single-sex schooling but the psychologists seem to object to it on philosophical rather than scientific grounds. "This country starts from the premise that educational experiences should be open to all and not segregated in any way," says Liben.  Well, no, I don't recall seeing that in the Constitution, because that means there should be no Advanced Placement classes.  I grew up in a tiny country boro - not even a village - and students were allowed to choose if they wanted to take more vocational courses, but Liben uses hot-button emotional verbage like 'segregated' even if the education is clearly more customized to the student body, like letting students who don't intend to go to college be 'segregated' so they can learn a trade.

And then there is the usual racism inference.  "The choice to fight sexism by changing coeducational practices or segregating by gender has parallels to the fight against racism," the researchers write in the paper. "The preponderance of social science data indicated that racially segregated schools promote racial prejudice and inequality."

Well, racism was not created in schools.  Schools are locally populated so when racism kept people living apart, it kept their schools apart.  Far more damage was done by forced integration in the South, and busing kids into other neighborhoods, than was done by separate schools.  

"The bottom line is that there is not good scientific evidence for the academic advantages of single-sex schooling," said Liben. "But there is strong evidence for negative consequences of segregating by sex -- the collateral damage of segregating by sex."

Studying preschoolers for a few weeks is hardly 'strong' evidence.  The fact is, if women are better educated when they are equal numbers or greater, and boys are unfazed by gender balanced, then single-sex education may be better for everyone.

If the researchers disagree, perhaps it is because they are in a field that is 70% women (one co-author out of eight is male) and it is skewing their perception.  Women in physics overwhelmingly contend they are uncomfortable in classes that are more men, and not because adult men suddenly learn prejudice against women in STEM fields.  Maybe women should be allowed to have a single-sex education if they choose and not be told they will learn (or reinforce) sexual stereotyping if that is the education they prefer.

But they claim any evidence of that is pseudoscience.  I am not sure it means what they think it means.

Citation: Diane F. Halpern, Lise Eliot, Rebecca S. Bigler, Richard A. Fabes, Laura D. Hanish, Janet Hyde, Lynn S. Liben, and Carol Lynn Martin, 'The Pseudoscience of Single-Sex Schooling', Science 23 September 2011: 1706-1707, DOI:10.1126/science.1205031