A prominent class of explanations for the gender gaps in student outcomes focuses on the interactions between students and teachers. In this study, I examine whether assignment to a same-gender teacher influences student achievement, teacher perceptions of student performance, and student engagement. This study's identification strategy exploits a unique matched-pairs feature of a major longitudinal study, which provides contemporaneous data on student outcomes in two different subjects. Within-student comparisons indicate that assignment to a same-gender teacher significantly improves the achievement of both girls and boys as well as teacher perceptions of student performance and student engagement with the teacher's subject. (Contains 9 tables and 8 footnotes.)