State and district leaders across the country are working intensely to respond to legislation calling for revised teacher evaluation systems that incorporate multiple measures of student learning and teacher practice. Whether through strengthened accountability or more formative support, the primary goal of this work is the continuous improvement of teaching and learning. To meet this goal, teacher evaluation systems need to be designed and implemented with teacher learning and development at their core, rather than appended later as an afterthought. Professional development is regularly associated with the "results" of evaluation, instead of recognized as an integral part of the evaluation process itself. Thus, the power of evaluation to generate greater teaching effectiveness is severely diminished. The purpose of this Research & Policy Brief is to support the thinking and efforts of state and district leaders who are designing and implementing evaluation systems that not only measure teaching effectiveness but generate it. The brief begins by describing the federal policy changes that animate this work. It then highlights the research on how teachers learn best, specifically how teachers learn from evaluation to generate increased teaching effectiveness. It also provides guidance on how to assess teachers' engagement in learning and collaboration to incentivize teachers' participation in job-embedded professional learning as well as to recognize and account for teachers' commitment to continuous improvement. Finally, the brief concludes with a description of the essential conditions for this important work. (Contains 2 tables.)