Concerned about the expense of teacher turnover, its disruption to schools and students, and its potential effect on students' access to effective teachers, the School District of Philadelphia partnered with the Regional Educational Laboratory Mid-Atlantic to better understand students' access to effective teachers and the factors related to teacher turnover. This analysis of differences in teacher effectiveness between and within schools in the district found that teachers of economically disadvantaged, Black, and Hispanic students had lower evaluation scores than teachers of non-economically disadvantaged and White students but similar value-added scores (a measure of teacher effectiveness based on student academic growth). The study also found that each year from 2010/11 through 2016/17, an average of 25 percent of the district's teachers left their school and 8 percent left the district. During the first five years of teaching, 77 percent of teachers left their school and 45 percent left the district. Turnover rates were highest for teachers who taught middle school grades, teachers who missed more than 10 days of school a year, teachers who identified as Black, teachers who had previously changed schools, and teachers who had low evaluation ratings. Teacher turnover was higher in schools where teachers had a less positive view of the school climate. School climate mattered more for teachers with higher evaluation ratings than for teachers with lower evaluation ratings. [For the study snapshot, see ED607753; for the appendices, see ED607754.]