Evaluation and the Local School District Monopsony
Kevin Carey has a smart post up about the NYT's release of value-added data for NYC teachers. Obviously, the "margin of error" question is an important one, but the bigger issue, to me, is the free-standing release of one piece of data that's intended to be part of a larger evaluation. No one can prevent newspapers from publishing this sort of data, but all the effort that's going into developing complex, multi-faceted teacher evaluations seems to be undermined if newspapers persist in publishing a single component. Will NYT and LAT continue to publish value-added data alone when new evaluation systems become available? Getting back to margins of error--Kevin makes solid points about how we think about the trade-offs here and our tendency to fear Type I errors more than Type II errors. I have to wonder if some of that tendency springs from the fact that the market for public school teacher talent has been something of a monopsony. Education policy debates tend to focus a lot on how the monopoly local school districts have historically held on provision of public education limits choices for students. But it's also true that the public school monopoly on provision, combined with traditional human capital practices in many districts, limits employment options for teachers in many locations--so a teacher who loses a position or just isn't a fit may have few alternative local employment options in their chosen profession (and probably don't want to move to Anaheim--never mind that certification might make it hard to do so). That makes the consequences more significant than in a more competitive labor market. One little-discussed effect of increasing diversity in public education provision is that it also increases teachers' choice of employers. In theory, this should have benefits, by improving teacher-school fit and creating competition among schools for high-quality teachers. In practice, it can also have downsides, particularly if weaker teachers wind up bouncing from school to school (as is the case among low-performing charters in some jurisdictions, particularly those where inequitable charter funding leads to lower wages).