Responding to an Illinois law that took effect in 2010, the Performance Evaluation Reform Act (PERA), Chicago Public Schools (CPS) created and implemented the REACH (Recognizing Educators Advancing Chicago's Students) educator evaluation and support system. REACH was piloted in 2012-13. It is still being implemented as of the 2019-20 school year, and will continue to be implemented through June 2024, per the teachers' contract agreed upon in fall 2019. The evaluation system includes classroom observation ratings of teacher practice, as well as up to two student growth measures. The stated goal of REACH is to provide valuable feedback to improve educators' professional practice and increase student learning. As with any professional evaluation system, a secondary use of REACH is to inform personnel decisions, such as classroom assignments, retention, tenure, remediation plans, and dismissal processes. In line with nationwide trends, almost all teachers in CPS received high evaluation ratings prior to REACH, and there was concern that such high levels of teacher performance were not translating into high levels of student learning. There was the potential that a more accurate rating system could make it easier to recognize and retain strong teachers while encouraging low-performing teachers to improve or exit. In light of this context, this brief answers the following research questions: (1) What proportion of teachers received high and low ratings under REACH, and how did that change over time? (2) How many low-rated teachers exited CPS or switched schools under REACH, compared to high-rated teachers?(3) How have classroom assignments within the school changed under REACH? This brief is part of a series of three to extend previous research from the University of Chicago Consortium on School Research (UChicago Consortium) on early REACH implementation and the REACH evaluation system five years after the 2012-13 rollout. [For "Teacher Evaluation in CPS: What Makes Evaluator Feedback Useful? Research Brief," see ED608091. For "Teacher Evaluation in CPS: Perceptions of REACH Implementation, Five Years In. Research Brief," see ED608094.]