A lousy way to evaluate teachers

Published in the  Chicago Sun Times, July 1, 2016

The Chicago Public Schools have decided that student scores on the PARCC test will be used as part of teacher evaluation ("PARCC will count in CPS teacher and school ratings," June 29).
Everything is wrong with this plan. 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 lousy way to do it.
Stephen Krashen

original article: http://chicago.suntimes.com/politics/parcc-count-cps-teacher-school-ratings/
this letter published at: http://chicago.suntimes.com/opinion/friday-letters-good-cops-dont-ignore-misdeeds/

Sources (not included in published letter)
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 http://www.nber.org/papers/w14607;