Friday, July 17, 2015

A lousy way to rate teachers

Sent to the Los Angeles Times, July 17

"Group sues 13 school districts for not using test scores in teacher evaluations,"(July 16) should stimulate discussion of whether using student test-score gains to evaluate teachers should remain state law. I suggest that the discussion include these two points:
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
Professor Emeritus, University of Southern California

original article:

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

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