[defertoreptar]

Here's one possible explanation:

> The vast majority of states adopted new high-stakes teacher evaluation systems between 2011 and 2016.

> We find that high-stakes evaluation reforms reduced the supply of newly licensed teachers by 16 to 18%.

> Evaluation reforms increased the probability a school had at least one unfilled teaching vacancy with effects concentrated in traditionally hard-to-staff schools.

> Evaluation reforms also increased the quality of new teachers by decreasing the supply of teachers coming from less competitive undergraduate institutions.

https://www.sciencedirect.com/science/article/abs/pii/S00472...