The gender agenda in many North American, Western European, and Australasian countries has undergone a "boy turn" in the past decade amid growing concerns about boys' apparent "underachievement" relative to girls. One aspect of this turn has been the resurrection of interest in single-sex classes in coeducational public state schools. This article reviews these developments from an international perspective, particularly focusing on the experiences of a number of United Kingdom secondary schools involved in the 4-year Raising Boys' Achievement Project. The article suggests that, while single-sex classes have the potential to raise the achievement levels of both boys and girls and to have a positive impact on the atmosphere and ethos for learning, these gains will be achieved only if the initiative is developed within gender-relational contexts rather than situated within recuperative masculinity policies. (Contains 4 tables, 1 figure and 16 notes.)