School performance pressures apply disproportionately to tested grades and subjects. Using longitudinal administrative data and teacher survey data from a large urban school district, we examine schools' responses to those pressures in assigning teachers to high-stakes and low-stakes classrooms. We find that teachers who produce greater student achievement gains in math and reading are more likely to be placed in a tested grade-subject combination in the following year and that the relationship between prior performance and assignment is stronger in schools where principals have more influence over assignments. This strategic response has the consequence of disadvantaging achievement in early grades, however, concentrating less effective teachers in K-2 classrooms, which in turn produces lower achievement for those students, as measured by low-stakes assessments, that may persist into tested grades as well.