The study reviewed in this paper examined whether the Chicago Public Schools' Teacher Advancement Program (Chicago TAP), which provides mentoring, leadership opportunities, and financial incentives to teachers, improved student academic achievement and teacher retention. The study used two designs to answer distinct research questions. Under the first design, a randomized controlled trial, the authors examined the academic achievement of more than 7,600 students in grades 4-8 from 34 public schools in Chicago. In the spring of 2007 and again in the spring of 2009, groups of schools were randomly assigned either to participate in Chicago TAP during the coming school year or to serve as a comparison group for a year and participate in Chicago TAP during the following school year. The effect of Chicago TAP on academic achievement after one year of implementation was estimated by comparing the spring math, reading, and science achievement of students in Chicago TAP schools to the achievement of students in schools that had not yet implemented the program. Using the second design, a quasi-experiment, the study examined teachers' retention rates, defined as remaining in the same school from year to year. The effect of Chicago TAP on teacher retention was assessed by comparing the retention of teachers in Chicago TAP schools with the retention of a matched sample of teachers in non-TAP Chicago public schools (sample sizes varied across years). After one year of implementation, students attending Chicago TAP schools did not score significantly differently in math, reading, or science achievement, as measured by the Illinois Standards Achievement Test (ISAT), than students attending comparison schools. Sixty-seven percent of teachers who were employed in schools that first implemented Chicago TAP in the fall of 2007 were still teaching in the same school in the fall of 2010. In contrast, 56% of teachers employed in non-TAP public schools were retained during the same period. This 12 percentage point difference in three-year teacher retention rates between the original cohort of Chicago TAP and non-TAP schools was statistically significant. The analysis of student academic achievement meets the What Works Clearinghouse (WWC) evidence standards with reservations. The analysis of teacher retention meets WWC evidence standards with reservations. Appended are: (1) Study details; (2) Outcome measures for each domain; (3) Study findings for each domain; and (4) Supplemental findings by domain. A glossary of terms is included. (Contains 3 endnotes.)