Administrative data on fifth grade students in North Carolina shows that more highly qualified teachers tend to be matched with more advantaged students, both across schools and in many cases within them. This matching biases estimates of the relationship between teacher characteristics and achievement; we isolate this bias in part by focusing on schools where students are distributed relatively evenly across classrooms. Teacher experience is consistently associated with achievement; teacher licensure test scores associate with math achievement. These returns display a form of heterogeneity across students that may help explain why the observed form of teacher-student matching persists in equilibrium. (Contains 8 tables, 3 figures and 44 footnotes.)