The Impact Evaluation of Teacher and Leader Performance Evaluation Systems (TLES Study) is a data collection that is part of the NCEE Evaluation Studies program. The TLES Study (https://ies.ed.gov/ncee/projects/evaluation/tq_performance.asp) is a cross-sectional data collection that evaluates the implementation of teacher and principal performance measures, as well as the impact of providing feedback based on these measures. Eight districts participated in the study; about 15 schools within each district were sampled. The data collection consisted of attendance lists, data from online systems, surveys of teachers and principals, ratings, classroom observations, student test scores, and district administrative records. Key findings produced from the TLES Study include: (1) the study's performance measures were implemented generally as planned, (2) the study's measures provided some information to identify educators who needed support, but provided limited information to indicate the areas of practice educators most needed to improve, (3) as intended, educators in treatment schools received more frequent feedback with ratings than did those in control schools, and (4)feedback from the study's measures had some positive impacts on teachers' classroom practice, principals' leadership, and student achievement.