“The long-run gains of not mixing genders in high-school classes” by Massimo Anelli, Giovanni Peri:

In a recent study (Anelli and Peri 2013) we ask if the gender composition of the high-school class attended by an individual affects his/her choice of study programme and subsequent long-term earning potentials. We use data that we collected on 30,000 students in Italian high schools over the period 1985-2005, including information on their high school, college career, family background and income as of 2005. We find that the gender ratio of high-school classmates significantly affected their choice of college major. In particular, women who attended a high-school class with a significant larger percentage of other female students (more than 75%) were significantly more likely to go on to choose college majors leading to high-paying jobs, namely engineering, economics, business and medicine. Those are also majors typically dominated by male students. On the other hand, female students in classes with a balanced gender mix were more likely to choose typically ‘female’ majors, that is, largely in the humanities and arts, and leading to lower earnings and limited overall career potential. …  If an objective of schooling is to increase women’s career opportunities and thereby their salaries, our results would suggest that gender-separated classrooms would be an effective step in the right direction. Incidentally, men will also benefit, being encouraged to enroll in high-earning majors.