Sunday, January 25, 2015

Not whether but how to evaluate teachers

Sent to The Economist, January 25, 2015

According to "America's New Advocacy," (January 24), "Many schools are in the grip of one of the most anti-meritocratic forces in America: the teachers’ unions, which resist any hint that good teaching should be rewarded or bad teachers fired."
This is incorrect: The objection is to how teachers are evaluated, specifically the use of student gains on standardized tests. A number of studies have shown that rating teachers using test score gains does not give consistent results. Different tests produce different ratings, and the same teacher’s ratings can vary from year to year, sometimes quite a bit.

In addition, using test score gains for evaluation encourages gaming the system, trying to produce increases in scores by teaching test-taking strategies, not by encouraging real learning. This is like putting a match under the thermometer and claiming you have raised the temperature of the room.

We are all interested in finding the best ways of evaluating teachers, but using student test-score gains is a very inaccurate way to do it.

Stephen Krashen

Some sources:
Different tests produce different ratings: Papay, J. 2010. Different tests, different answers: The stability of teacher value-added estimates across outcome measures. American Educational Research Journal 47,2.
Vary from year to year: Sass, T. 2008. The stability of value-added measures of teacher quality and implications for teacher compensation policy. Washington DC: CALDER. (National Center for Analysis of Longitudinal Data in Educational Research.) Kane, T. and Staiger, D. 2009. Estimating Teacher Impacts on Student Achievement: An Experimental Evaluation. NBER Working Paper No. 14607;

Original article:

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