There is growing concern among policy makers over the quality of the teacher workforce in general, and the distribution of effective teachers across schools. The impact of teacher attrition on overall teacher quality will depend on the effectiveness of teachers who leave the profession. Likewise, teacher turnover may alleviate or worsen inequities in the distribution of teachers, depending on which teachers change schools or leave teaching and who replaces them. Using matched student--teacher panel data from the state of Florida, we examine teacher mobility across the distribution of effectiveness (as measured by teacher value added). We find that top-quartile and bottom-quartile teachers exit at a higher rate than do average-quality teachers. Additionally, as the share of peer teachers with more experience, advanced degrees, or professional certification increases, the likelihood of moving within-district decreases. We also find some evidence of assortative matching among teachers--more productive reading/language arts teachers are more likely to stay in teaching if they have more productive peer teachers.