Single-sex schooling has very small benefits, according to a meta-analysis of 184 studies representing 1.6 million students in K-12 across 21 nations. Because U.S. students aren’t randomly assigned to single-sex classes, it’s hard to find good control groups here, notes cognitive scientist Dan Willingham.
In controlled studies, there were statistically reliably, but numerically quite modest positive effects of single-sex classrooms for both boys and girls in mathematics achievement, science achievement, and verbal achievement. Girls showed an edge in single-sex classes for math attitude, science achievement, and overall academic achievement, but again, the gains were modest. If one restricts the analysis to U.S. students, virtually all of these small effects disappear.
There was no effect for attitudes towards school, gender stereotyping, educational aspirations, self-concept, interpersonal relationships, or body image.
For any one child, single-sex schooling might be helpful, writes Willingham. Overall, not so much.