What’s the evidence? What have researchers found when they compare single-sex education with coeducation?
Let’s begin with two recent studies in which students were RANDOMLY assigned either to single-gender or coed classrooms, with no opt-out. We are aware of no other studies in which students were randomly assigned either to single-gender or coed classrooms, with no parental opt-out allowed. Any such study would be illegal in the United States; in the United States, federal statute 34 CFR 106.34 requires that any assignment to a single-gender classroom or school must be completely voluntary.
In the first study, researchers from 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 any 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.