Principals tend to prefer working in schools with higher-achieving students from more advantaged socioeconomic backgrounds. Principals often use schools with many poor or low-achieving students as stepping stones to what they view as more desirable assignments. District leadership can also exacerbate principal turnover by implementing policies aimed at improving low-performing schools such as rotating school leaders. Using longitudinal data from one large urban school district we find principal turnover is detrimental to school performance. Frequent turnover results in lower teacher retention and lower student achievement gains, which are particularly detrimental to students in high-poverty and failing schools. (Contains 10 tables and 3 footnotes.)