Is the gender gap in school performance affected by the sex of the teacher?

Girls outperform boys in school. We investigate whether the gender performance gap can be attributed to the fact that the teacher profession is female dominated, that is, is there a causal effect on student outcomes from having a same-sex teacher? Using data on upper-secondary school students and their teachers from the municipality of Stockholm, Sweden, we find that the gender performance differential is larger in subjects where the share of female teachers is higher. We argue, however, that this effect can not be interpreted as causal, mainly due to teacher selection into different subjects and non-random student-teacher matching. Exploring the fact that teacher turnover and student mobility give rise to variation in teacher's gender within student and subject, we estimate the effect on student outcomes of changing to a teacher of the same sex. We find no strong support for our initial hypothesis that a same-sex teacher improves student outcomes.