The Mirage: Confronting the Hard Truth About Our Quest for Teacher Development argues for fundamental changes in the way public school districts think about teacher growth. Using original data collected from teachers and administrators in three public districts and one charter network, the authors contend that although the public districts invest heavily in teacher professional development, what is offered is often a poor fit to teacher needs and ultimately ineffective as a means to improving teacher evaluation scores. Many descriptive portions of this study are strong – including evidence that public district teachers are doubtful about the utility of their own professional development and that public district offerings often lack coherence. The per-teacher cost estimate for professional development, however, was calculated by including teacher salary increases that result from professional development credits and master’s degrees, a choice at odds with much of the prior research on this topic. As well, the analysis comparing growth in teacher evaluation scores to teachers’ professional development experiences suffers from a number of issues, including a mis-match between the behaviors rewarded by teacher evaluation and the professional development features explored in this study. That said, readers who rely more on the report’s empirical evidence and less on its hyperbolic statements will profit from reading this report.