Rhee brings high-powered incentives to DC's schools

So Michelle Rhee, DC's controversial chancellor, just fired 241 teachers, most due to poor performance on new IMPACT evaluations.  That's about 6 percent of all teachers in the district.  Another 737 were rated "minimally effective" on IMPACT and could lose their jobs next year.

At least the recession, high unemployment and state cutbacks around the country have left plenty of jobless teachers to fill the new vacancies in DC.

So, should economists everywhere cheer a new high-powered incentive system for teachers?

I'm not so sure.  Incentives can be great.  But they have to be meaningful.

One encouraging sign is that a lot of thought and effort seemed to go into developing IMPACT (see here and here). The problem with IMPACT is that it hasn't yet been proven meaningful.  Why, I wonder, wasn't the evaluation system first tested experimentally to see if it actually differentiated effective teachers from ineffective teachers?

Teaching effectiveness is an iellusive thing.  This recent paper in the Journal of Political Economy, for example, shows that teachers that provoke "deep learning," measured by performance of students in courses subsequent to the course being evaluated, tend to score relatively poorly on current evaluations.  This is the best metric for good teaching I've seen: not student performance in the current class, standardized tests, or current evaluations, but performance in subsequent classes that require or otherwise use or apply knowledge from the course being evaluated.  Granted, this JPE study was for college students and things might be different for kindergarten through 12th grade.

Still, I would have like to have seen IMPACT ratings carefully studied over time in relation to actual student performance before they started laying off teachers.  Yes, this kind of careful investigation takes time.  But without it efforts to improve DC education are a lot less likely to succeed.

Update: Speaking about the iellusiveness of teaching effectiveness, this study, as described by David Leonhardt, is kind of mind blowing.  But you know, it's what my mother (a child development expert who taught Kindergarten for 9 years) always told me.