Teaching may be the most-scrutinized occupation in the economy. Over the past four decades, empirical researchers—many of them economists—have accumulated an impressive amount of evidence on teachers: the heterogeneity in teacher productivity, the rise in productivity associated with teaching credentials and on-the-job experience, rates of turnover, the costs of recruitment, the relationship between supply and quality, the effect of class size and the monetary value of academic achievement gains over a student's lifetime. Since the passage of the No Child Left Behind Act, along with a number of state-level educational initiatives, the data needed to estimate individual teacher performance based on student achievement gains have become more widely available. However, there have been relatively few efforts to examine the implications of this voluminous literature on teacher performance. In this paper, we ask what the existing evidence implies for how school leaders might recruit, evaluate, and retain teachers.