Evaluating Teacher Evaluations

by Linda Darling-Hammond, Audrey Amrein-Beardsley, Edward Haertel, and Jesse Rothstein

(The Phi Delta Kappan, March 2012)

Practitioners, researchers, and policy makers agree that most current teacher evaluation systems do little to help teachers improve or to support personnel decision making. There's also a growing consensus that evidence of teacher contributions to student learning should be part of teacher evaluation systems, along with evidence about the quality of teacher practices.  "Value-added models" (VAMs), designed to evaluate student test score gains from one year to the next, are often promoted as tools to accomplish this goal.

Value-added models enable researchers to use statistical methods to measure changes in student scores over time while considering student characteristics and other factors often found to influence achievement.  In large-scale studies, these methods have proved valuable for looking at factors affecting achievement and measuring the effects of programs or interventions.

Using VAMs for individual teacher evaluation is based on the belief that measured achievement gains for a specific teacher's students reflect that teacher's "effectiveness." This attribution, however, assumes that student learning is measured well by a given test, is influenced by the teacher alone, and is independent from the growth of classmates and other aspects of the classroom context.  None of these assumptions is well supported by current evidence.

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