Researchers at the University of Pennsylvania traveled to Seoul South Korea, because in Seoul, students are RANDOMLY assigned either to single-gender or to coed high schools. The assignment is truly random, and compulsory. Students cannot “opt out” of either the single-gender format or the coed format. This policy of random assignment was instituted in 1974 specifically to prevent clustering of students from particular backgrounds at particular schools. In recent decades, many Korean school districts have loosened the policy and they now allow parents to express preferences or to “opt out” of particular schools. But not in Seoul. In Seoul, it’s still a true random assignment with no opt-out.
The scholars from Penn recognized that the random nature of the assignment creates the opportunity to compare single-gender schools with coed schools, without the usual confounding variables which would accompany any attempt at a similar comparison among North American schools. All the schools in the study are publicly-funded; none of them charges fees or tuition. The researchers found no differences between the single-gender and the coed schools in terms of teacher quality or in teacher training. Class sizes in the boys’ schools were no different than in the typical coed school, and class sizes were actually slightly larger in girls’ schools than in the typical coed school. There were no differences in socioeconomic background or prior academic achievement between students attending single-gender schools and those attending coed schools.
What were the results? Girls attending girls’ schools were significantly more likely to attend a 4-year college compared with girls attending coed schools (Cohen’s d = 0.5, p < 0.01). Likewise, boys who graduated from boys’ schools were significantly more likely to attend a 4-year college compared with boys who graduated from coed schools (Cohen’s d = 0.8, p < 0.01). All these effects remain significant after controlling for eligibility for free school lunches, prior academic achievement, and other demographic and student parameters. Boys at boys’ schools also earned significantly higher test scores compared with boys at coed schools; likewise, girls at girls’ schools also earned significantly higher test scores compared with girls at coed schools. The authors conclude:
Our analyses show that single-sex schools are causally linked with both college entrance exam scores and college-attendance rates for both boys and girls. Attending all-boys schools or all-girls schools, rather than attending coeducational schools, is significantly associated with higher average scores on Korean and English test scores. Compared with coeducational schools, single-sex schools have a higher percentage of graduates who moved on to four-year colleges.
Go to http://repository.upenn.edu/psc_working_papers/15/,
then click on “Download” on the right to read more.