The term "teacher retention" refers to the ability to keep teachers on the job. In other words, it is the ability to reduce or eliminate teacher turnover. "Turnover" refers to the migration of teachers between schools or districts "and" the attrition of teachers from the profession (Ingersoll & Perda, 2009). From the perspective of a principal, both are problems of equal concern. From the perspective of a policymaker seeking to improve teacher quality systemwide, however, it is a more nuanced concern. One principal's turnover may be another principal's recruitment boon. If the latter principal is leading a hard-to-staff school, such migration may be welcomed as a move toward a more equitable distribution of teachers. Both migration and attrition are costly, with taxpayers losing approximately $2.2 billion per year to teacher migration and $2.7 billion per year to teacher attrition (Alliance for Excellent Education, 2005). Although the retention of ineffective teaches should of course be discouraged, increasing the retention of effective teachers in the profession will serve all principals well. In high-needs districts, where teacher turnover tends to be highest, improving teacher retention is particularly important. Tracking the movement of teachers between schools, districts, and states as well as into and out of the profession is a good first step to help policymakers and school leaders develop effective strategies for improving teacher retention. This Key Issue offers strategies to improve the retention of qualified and effective teachers in hard-to-staff schools.