The idea that students would learn better in single-sex classrooms seems logical. The typical arguments include

• Boys find girls more distracting in class than they find other boys. Likewise, girls find boys more distracting.
• Sex differences in math and science achievement are a product of social influence. Those influences will be reduced or eliminated if girls are in classrooms only with girls.
• Boys dominate classroom discussion, and so girls are denied practice in articulating and defending their views.
• Boys and girls have different brains, and therefore learn differently. If they are taught separately, teachers can tune their instruction to the way each sex learns.

The last of these is frequently overwrought and over-interpreted, but generally, these reasons seem plausible. But that obviously doesn't prove that single-sex education confers any advantage to students.

A 2005 report written for the Department of Education (Mael et al, 2005) reported mixed effects, but generally a positive conclusion for single-sex classrooms in short-run academic outcomes. There was no indication of a boost to longer-term outcomes.

A new study (Pahlke, Hyde, & Allison, 2014) reports a meta-analysis of 184 studies representing 1.6 million students in K-12 across 21 nations. The authors place considerable emphasis on the problem of control in this research. They end up concluding that, with proper controls, analyses show that single-sex classrooms don't help students much.

The challenge in this sort of work is that comparisons of single-sex and coed classrooms often do not use random assignment. Students (or parents) choose a single-sex classroom. So for this review, the authors distinguished between controlled experiments (the original study either used random assignment or made some attempt to measure and statistically account for associated variables) and uncontrolled studies.

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 (Hedges g in all cases less than 0.10). 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.

There were not enough controlled studies to examine aggression, body image, interpersonal relations, interest in STEM careers, science attitudes, or victimization.

It's also notable that there was no dosage effect: the advantage was no larger when all classes within a school were single-sex classes, compared to when a single class was.

The authors were also interested in evaluating whether single sex classes were effective for boys of color. They reported that there were not enough controlled studies to answer this question, but even restricting the analysis to uncontrolled studies, the effects were minimal.

When you consider the factors that we know contribute substantially to academic attitudes and performance--the student's prior academic achievement, the curriculum, the home environment, the teacher's skill--it's easy to believe that the sex of the other students would have a modest effect, if any.

That said, it could be that a single sex school has a profound influence on a few students. A few years ago, friends of mine moved their 15 year old daughter to an all-girls school because she was "boy crazy." According to my friends, she didn't become any less interested in boys, but she did focus on work better during school hours. But then again it's possible my friends were kidding themselves.

References

Mael, F., Alonso, A., Gibson, D., Rogers, K., & Smith, M. (2005).
Single-sex versus coeducational schooling: A systematic review. Washington, DC: American Institutes for Research

Pahlke, E.,Hhyude, J. S, & Allison, C. M. (2014). The effects of single-sex cmopared with coeducational schooling on students' performance and attitudes: A meta-analysis. Psychological Bulletin, Advance online publication, http://dx.doi.org/10.1037/a0035740

Important study on the impact of education on women's attitudes and beliefs:

Mocan & Cannonier (2012) took advantage of a naturally-occurring "experiment" in Sierra Leone. The country suffered a devastating, decade-long civil war during the 1990s, which destroyed much of the country's infrastructure, including schools. In 2001, Sierra Leone instituted a program offering free primary education; attendance was compulsory.

This policy provided significant opportunities for girls who were young enough for primary school, but none for older children. Further, resources to implement the program were not equivalent in all districts of the country.  The authors used these quirky reasons that the program was more or less accessible to compare girls who participated and those who did not. (Researchers controlled for other variables such as religion, ethnic background, residence in an urban area, and wealth.)

The outcome of interest was empowerment, which the researchers defined as "having the knowledge along with the power and the strength to make the right decisions regarding one's own well-being."

The outcome measures came from a 2008 study (the Sierra Leone Demographic and Health Survey) which summarized interviews with over 10,000 individuals.

The findings:

Better educated women were more likely to believe

• a woman is justified in refusing sex with her husband if she knows he has a sexually transmitted disease
• that a husband beating his wife is wrong
• that female genital mutilation is wrong

Better educated women were more likely to endorse these behaviors:

• having fewer children
• using contraception
• getting tested for AIDS

One of the oddest findings in these data is also one of the most important to understanding the changes in attitudes: they are not due to changes in literacy. The researchers drew that conclusion because an increase in education had no impact on literacy, likely because the quality of instruction in schools was very low. The best guess is that the impact of schooling on attitudes was through social avenues.

Mocan, N. H. & Cannonier, C. (2012) Empowering women through education: Evidence from Sierra Leone. NBER working paper 18016.

In primary school, a student's relationship with his or her teacher has a significant impact on the student's academic progress. Students with positive relationships are more engaged and learn more (e.g., Hughes et al, 2008). In addition, teachers are more likely to have negative relationships with boys than with girls (e.g., Hamre & Pianta, 2001).

Previous research has not, however, accounted for the gender of the teacher. Perhaps conflict is more likely when teacher and student are of different sexes, and because there are more female than male teachers, we end up concluding that boys tend not to get along with their teachers.

A new study (Split, Koomen & Jak, in press) indicates that's not the case.

This appears to be the first large-scale study that examined teacher-student relationships in primary school while accounting for the sex of teachers.

Teachers completed questionnaires about their relationships with their students. The questionnaires measured three constructs:

• Closeness Warmth and open communication. Sample item "If upset, this child will seek comfort from me."
• Conflict Negative interactions, need for the teacher to correct student behavior. Sample item "This child remains angry or resentful after being disciplined."
• Dependency Clinginess on the part of the student; sample item "This child asks for my help when he or she really does not need help."

All in all, the data did not support the idea that boys connect emotionally  with male teachers.

For Closeness, female teachers generally felt closer to their students than male teachers. Male teachers did not feel closer to either boys or girls, but female teachers felt closer to girls than they did to boys.

For Conflict, female teachers reported less conflict than male teachers did. Both male and female teachers reported less conflict with girls than with boys.

For Dependency, female teachers reported less dependency than male teachers did. There were no differences among boys and girls on this measure.

This research has been difficult to conduct, simply because most groups of teachers don't have enough male teachers in elementary grades to conduct a meaningful analysis. This is just one study, but the results indicate that all teachers--male and female--have a tougher time with boys. More conflictual relationships are reported with boys than with girls, and female teachers report less close relationships with boys.


Hamre, B. K., & Pianta, R. C. (2001). Early teacher–child relationships and the  trajectory of children's school outcomes through eighth grade. Child Development, 72, 625–638.

Hughes, J. N., Luo, W., Kwok, O. M., & Loyd, L. K. (2008). Teacher–student support, effortful engagement, and achievement: A 3-year longitudinal study. Journal of Educational Psychology, 100, 1–14.

Split, J. L., Koomen, H. M. Y., & Jak, S. (in press) Are boys better off with male and girls with female teachers? A multilevel investigation of measurement invariance and gender match in teacher-student relationship quality. Journal of School Psychology.