Educators raise concerns about what happens to students when they are exposed to new or new-to-school teachers. However, even when teachers remain in the same school they can switch roles by moving grades and/or subjects. We use panel data from New York City to compare four ways in which teachers are new to assignment: new to teaching, new to district, new to school, or new to subject/grade. We find negative effects of having a churning teacher of about one third the magnitude of the effect of a new teacher. However the average student is assigned to churning teachers four times more often than to new teachers, and historically underserved students are slightly more likely to be assigned to churning teachers.