One of the most important things school systems can do to promote student achievement is to ensure that all students have effective teachers. Effective teachers may be particularly important for the most disadvantaged students. The U.S. Department of Education commissioned the American Institutes for Research (AIR) to create this report as a resource for state and district policymakers who are working to ensure that all students, regardless of background, have effective teachers. This report is intended to illustrate the steps districts take and the challenges they face in assessing teacher effectiveness as a precursor to providing effective teachers for all students. In so doing, the report focuses on three areas of state and district policy that play a mutually reinforcing role in promoting equitable access to effective teachers: (1) Identifying effective teachers; (2) Using information about teacher effectiveness in human resource policies; and (3) Using information about teachers' effectiveness in efforts to ensure equity. This report draws on the experiences of five districts to provide examples that may be relevant to state and district policymakers considering action in these three areas. The five districts are: (1) Columbus City Schools (Ohio); (2) Eagle County Schools (Colorado); (3) Hamilton County Public Schools (Tennessee); (4) Hillsborough County Public Schools (Florida); and (5) Houston Independent School District (Texas). The report addresses three questions: (1) How did the districts identify effective teachers and what were some of the challenges associated with the measures that the districts used?; (2) How did the districts use information about teachers' effectiveness in human resource policies?; and (3) How did the districts use information about teachers' effectiveness in their efforts to make the distribution of effective teachers more equitable? By summer 2010, all five districts had begun to measure teacher effectiveness through student achievement growth in at least some schools and most were implementing new classroom observations of teachers' practice. By summer 2010, the five districts had used those measures in human resource policies in a variety of ways, and some had other policies in place for promoting equitable access to effective teachers. AIR staff visited each district in June and July of 2010 to learn about their specific approaches to teacher effectiveness, including the way the districts selected those approaches and resolved key dilemmas and challenges. This report highlights examples of the way study districts identified effective teachers, and draws on that information for human resource policies and efforts to ensure equity. Because most of the practices discussed in this report are relatively new and will likely be refined over time, monitoring and evaluation will allow districts and states to determine whether their actions are successful and to adjust their practices accordingly.