A growing body of research recognizes the critical role of the school principal, demonstrating that school principals' effects on student outcomes are second only to those of teachers. Yet policy makers have often paid little attention to principals, choosing instead to focus policy reform on teachers. In the last decade, this pattern has shifted somewhat. Federal policies such as Race to the Top (RTTT) and Elementary and Secondary Education Act waivers emphasized principal quality and prompted many states to overhaul principal evaluation as a means to develop principals' leadership practices and hold them accountable for the performance of their schools. The development and dissemination of principal evaluation policies has proceeded rapidly, however, it is unclear whether focusing on principal evaluation has targeted the most impactful policy lever. In this policy brief, we describe where policy makers have placed their bets in post-RTTT principal evaluation systems and comment on the wisdom of these wagers. We describe the degree to which principal evaluation components, processes, and consequences vary across the fifty states and the District of Columbia, and review evidence on which aspects of principal evaluation policies are most likely to improve principals' practice and hold them accountable.