Many of them began separating the sexes because of a belief that boys and girls should be taught differently that grew out of popular books, speeches and workshops by Michael Gurian, Leonard Sax and others.

Dr. Sax, executive director of the National Association of Single Sex Public Education, was singled out for criticism in the Science article, for his teachings that boys respond better to energetic, confrontational classrooms while girls need a gentler touch.

“A loud, cold classroom where you toss balls around, like Dr. Sax thinks boys should have, might be great for some boys, and for some girls, but for some boys, it would be living hell,” Dr. Halpern said in an interview. She said that while girls are better readers and get better grades, and boys are more likely to have reading disabilities, that does not mean that educators should use the group average to design different classrooms. “It’s simply not true that boys and girls learn differently,” she said. “Advocates for single-sex education don’t like the parallel with racial segregation, but the parallels are there. We used to believe that the races learned differently, too.”

Dr. Sax criticized the article on many counts, and said it did not fairly reflect his current views. He vehemently rejected the comparison to racial segregation, and the use of the term “sex segregation.” Legally, race is a suspect category, while sex is not.

“We are not asserting that every child should be in a single-sex classroom, we are simply saying that there should be a choice,” Dr. Sax said in an interview.

The authors of the article, though, say that because there is no good scientific research backing such a choice, the government cannot lawfully offer single-sex education in public schools.

The article cites a review commissioned by the Education Department, comparing single-sex and coed outcomes, concluding that, “as in previous reviews,” the results are equivocal.