The prevalence of women in the teaching profession has been claimed by various scholars to be responsible for the low school performance among boys. Based on this claim there have been widespread calls for increasing the share of male teachers as a means of improving boys' school performance. There is, however, very little empirical evidence supporting the claim that boys do in fact benefit from being taught by male teachers. Drawing on data from the 2007 Trends in International Mathematics and Science Study and the 2006 Progress in International Reading Literacy Study, this paper examines the relationship between teacher gender and boys' and girls' respective school performance in a sample of 146,315 elementary school students from 21 countries. It finds that boys do not benefit from being taught by male teachers, neither in mathematics nor in reading. In some countries, however, girls seem to profit from being taught by female teachers. (Contains 2 notes and 4 tables.)