D.C. Teacher Evaluation Scores Flawed

by Diane Ravitch, 12/23/13
Last Friday, officials at the central office of the District of Columbia Public Schools quietly released the news that the teacher ratings on its highly touted IMPACT system contained errors. It was not clear how many teachers were affected. If you want to bury a policy disaster, the best time to announce it is on a Friday before a long holiday, on the assumption it will be ignored and forgotten.

Researchers have warned for the past three years that grading teachers by the test scores of their students is error-ridden, inaccurate, and unstable. Earlier this year, the distinguished psychometrician Edward Haertel of Stanford warned in a major lecture that value-added scores should not be used as a fixed percentage when evaluating teachers and should have multiple safeguards to avoid error. Did anyone at the U,S. Department of Education or anywhere else take heed? Of course not.

As Valerie Strauss notes in the linked article, this inherently flawed and demoralizing process has been widely accepted (it is a major element of Race to the Top; in addition, states that want waivers from the impossible mandates of NCLB must agree to adopt this procedure, no matter how ill-conceived it is.)

Strauss writes:

“Testing experts have long warned that using test scores to evaluate teachers is a bad idea, and that these formulas are subject to error, but such evaluation has become a central part of modern school reform. In the District, the evaluation of adults in the school system by test scores included everybody in a school building; until this year, that even included custodians. In some places around the country, teachers received evaluations based on test scores of students they never had. (It sounds incredible but it’s true.)”

Only a few weeks ago, Audrey Amrein-Beardsley wrote on her blog that the ratings on the D.C. IMPACT system made no sense.

Now the company that created the rating system has acknowledged the errors.

Let’s see if some enterprising journalist digs into this fiasco.