Value-added: An important measure

A fantastic study published by the Brookings Institute called “Evaluating Teachers: The Important Role of Value-Added,” explores the benefits and challenges of a system that evaluates teachers by their students improvement on objective measures like standardized tests.

Here are the main points of the study and discussion:

Current evaluation systems that use principals to evaluate teachers end up classifying 99 percent of teachers as effective. Obviously principal evaluations alone cannot accurately determine a teacher’s effectiveness.

Value-added is “not a perfect system of measurement,” but it can “complement” other measurements like parent and student feedback, observations, and self assessments.

Many teachers are skeptical of value-added systems because they are afraid of being labeled as bad teachers solely because of their students’ test scores. “But framing the problem in terms of false negatives places the focus almost entirely on the interests of the individual who is being evaluated rather than the students who are being served. It is easy to identify with the good teacher who wants to avoid dismissal for being incorrectly labeled a bad teacher. From that individual’s perspective, no rate of misclassification is acceptable.”

The authors of this study illustrate the problem with this argument well when they point out that SAT scores are only moderately correlated to success in college, and between-season batting averages for baseball players are only moderately correlated to professional batting averages. Nevertheless, we use these measurements because they are the best we have. In the authors’ words, “We should not set unrealistic expectations for the reliability or stability of value-added. Value-added evaluations are as reliable as those used for high stakes decisions in many other fields.”

Value-added measurements are especially important when we examine the alternatives for measuring teacher performance: seniority (experience) or principal evaluations. This study finds that value-added measurements are the best way to determine effectiveness.

Teachers are worried that value-added indicators unfairly measure their effectiveness. While it is true that value-added will not be a perfect measure, it is still an important one. Combining an objective measure of student performance with more objective measurements is the only way to create a fair and comprehensive evaluation system.