Revisiting The “5-10 Percent Solution”
In a post over a year ago, I discussed the common argument that dismissing the “bottom 5-10 percent” of teachers would increase U.S. test scores to the level of high-performing nations. This argument is based on a calculation by economist Eric Hanushek, which suggests that dismissing the lowest-scoring teachers based on their math value-added scores would, over a period of around ten years (when the first cohort of students would have gone through the schooling system without the “bottom” teachers), increase U.S. math scores dramatically – perhaps to the level of high-performing nations such as Canada or Finland.*
This argument is, to say the least, controversial, and it invokes the full spectrum of reactions. In my opinion, it’s best seen as a policy-relevant illustration of the wide variation in test-based teacher effects, one that mightsuggest a potential of a course of action but can’t really tell us how it will turn out in practice. To highlight this point, I want to take a look at one issue mentioned in that previous post – that is, how the instability of value-added scores over time (which Hanushek’s simulation doesn’t address directly) might affect the projected