Since the mid-1990s, considerable concern has been expressed about the feminization of education. The underlying assumption is that the increasing number of female teachers is leading to a lack of male role models, which may then have negative consequences for the achievement and behaviour of boys in particular. For this reason, policy is currently being pursued in several countries to increase the number of male teachers. In the present article, the theoretical foundation for this policy will be shown to be weak at best. To test this empirically, a large-scale study of Dutch primary schools was conducted, which involved 5181 grade eight pupils, 251 teachers and 163 schools. This study confirmed that teacher sex has no effect whatsoever on the achievement, attitudes or behaviour of pupils. This finding holds for both boys and girls, for both minority and non-minority pupils and for both children from lower and higher social-economic milieus.