There are fierce debates over the best way to prepare teachers. Some argue that easing entry into teaching is necessary to attract strong candidates, while others argue that investing in high quality teacher preparation is the most promising approach. Most agree, however, that we lack a strong...

In practice, teacher turnover appears to have negative effects on school quality as measured by student performance. However, some simulations suggest that turnover can instead have large, positive effects under a policy regime in which low-performing teachers can be accurately identified and...