How to improve the assignment to remedial classes.

A great new NBER working paper on using evidence and prediction to improve the way students are sorted in remedial college classes to improve their graduation rates. From the abstract: 

Our analysis uses administrative data and a rich predictive model to examine the accuracy of remedial screening tests, either instead of or in addition to using high school transcript data to determine remedial assignment. We find that roughly one in four test-takers in math and one in three test-takers in English are severely mis-assigned under current test-based policies, with mis-assignments to remediation much more common than mis-assignments to college-level coursework.

The conventional wisdom seems to be that putting students who are ill-prepared for college-level work in regular classes is bad because (1) they'll likely fail, (2) they'll become frustrated and will drop out of school altogether. But the other side, the case of putting students who are capable of handling college work in remedial classes, doesn't, on its face, seem as terrible of a cost — so what, students spend an extra semester on foundational material, this'll help them be even more prepared for rigorous college work. 

Students who are unchallenged will become unmotivated and may do worse, even in easier classes. See, e.g., this study from UChicago which found an algebra-for-all policy hurt high achievers because of mixed-ability classrooms. High, low, and middle ability students all deserve the highest quality education.

Algebra-for-all isn't prima facie a bad policy; remedial college classes are not prima facie terrible. As always, though, it comes down to implementation. And it's nice to see some real empirical work to compare treatments to find the right mix.