All that stuff you hear about how teachers unions protect bad teachers through the evils of due process and their general uniony badness? A new study for the National Bureau of Economic Research says nuh-uh. EduShyster interviews the study’s author, Eunice Han:

By demanding higher salaries for teachers, unions give school districts a strong incentive to dismiss ineffective teachers before they get tenure. Highly unionized districts dismiss more bad teachers because it costs more to keep them. Using three different kinds of survey data from the National Center for Education Statistics, I confirmed that unionized districts dismiss more low-quality teachers than those with weak unions or no unions. Unionized districts also retain more high-quality teachers relative to district with weak unionism. No matter how and when I measured unionism I found that unions lowered teacher attrition.

This isn’t all theoretical. Thanks to Republican state governments in Indiana, Idaho, Tennessee, and Wisconsin, Han had the chance to see how this played out in recent years:

If you believe the argument that teachers unions protect bad teachers, we should have seen teacher quality rise in those states after the laws changed. Instead I found that the opposite happened.

Funny how all that rhetoric about teachers unions keeping illiterate monsters in the classroom turns out to be false. Don’t hold my breath waiting for this myth to drop out of the Republican narrative about education, though.