Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Class-size reduction (CSR) policies have typically failed to produce large achievement gains. One common explanation is that CSR forces schools to hire low-quality teachers. Prior studies of this hypothesis have been hindered by poor data. Using different data, we find that hiring quality did fall with state-wide CSR. However, this drop was temporary due to attrition by the lowest performers. Furthermore, the drop was similar for schools classified as treated and control for prior evaluations of CSR. Therefore, differences in the quality of incoming teachers cannot explain the estimated performance of CSR. This is consistent with hiring spillovers in connected markets.