Measuring Teacher Effectiveness: Credentials Unrelated to Student Achievement

Given the challenges facing American public education today, identifying effective teachers is a more vital task than ever before. A wide body of research shows that teachers are the most important school-based factor related to student achievement. Policymakers and taxpayers want to know what factors create effective teachers—not only for the sake of their own children’s educations but also because teacher salary and benefits represent the nation’s single largest educational expenditure. And school administrators need to identify teachers who will be successful over the long term before those teachers earn the ironclad job protection of tenure.

In the U.S. public school system today, the method used to determine teacher effectiveness—and thus to drive salary, promotion, and tenure decisions—is based on a few external credentials: certification, advanced degrees, and years of experience in the classroom. Yet according to a new analysis of student performance in Florida that two colleagues and I conducted, little to no relationship exists between these credentials and the gains that a teacher’s students make on standardized math and reading exams. Our expansive study included all test-taking public elementary school students in the state of Florida over a period of four years.

Our study, to be published in the peer-reviewed journal Economics of Education Review, builds on two decades of research from a variety of school systems and confirms a consistent finding: external teacher credentials tell us next to nothing about how well a teacher will perform in the classroom. Such research has not, however, yet had a substantial effect on the practices of U.S. public schools. Today’s public school system continues to rely on external teacher credentials to decide who gets to teach and how much a teacher is paid. Though the debate over how most accurately to use statistical measures to identify teacher quality is far from completed, the general finding that there is a vast difference between the system’s best and worst teachers is no longer in serious dispute. The large body of research on teacher quality suggests that a new method of identifying the best teachers is needed—one that focuses on measuring the contributions that teachers actually make in the classroom.

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