Teacher Effects on Student Achievement and Height: A Cautionary Tale
Estimates of teacher “value-added” suggest teachers vary substantially in their ability to promote student learning. Prompted by this finding, many states and school districts have adopted value-added measures as indicators of teacher job performance. In this paper, we conduct a new test of the validity of value-added models. Using administrative student data from New York City, we apply commonly estimated value-added models to an outcome teachers cannot plausibly affect: student height. We find the standard deviation of teacher effects on height is nearly as large as that for math and reading achievement, raising obvious questions about validity. Subsequent analysis finds these “effects” are largely spurious variation (noise), rather than bias resulting from sorting on unobserved factors related to achievement. Given the difficulty of differentiating signal from noise in real-world teacher effect estimates, this paper serves as a cautionary tale for their use in practice.
We thank the NYC Department of Education and Michelle Costa for providing data. Amy Ellen Schwartz was instrumental in lending access to the Fitnessgram. Greg Duncan, Avi Feller, Richard Startz, Jim Wyckoff, Dean Jolliffe, Richard Buddin, George Farkas, Sean Reardon, Michal Kurlaender, Marianne Page, Susanna Loeb, Jesse Rothstein, Jeff Smith, Howard Bloom, and seminar participants at Teachers College Columbia University, Stanford CEPA, Irvine Network on Interventions in Development, and APPAM provided helpful comments. Siddhartha Aneja, Annie Laurie Hines, and Danea Horn provided outstanding research assistance. All remaining errors are our own. Research reported in this publication was supported by the Eunice Kennedy Shriver National Institute of Child Health & Human Development of the National Institutes of Health under Award Number P01HD065704. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health or the National Bureau of Economic Research.