Teacher Layoffs: An Empirical Illustration of Seniority vs. Measures of Effectiveness. Brief 12

Abstract

This policy brief, a quick look at some aspects of the debate, illustrates the differences in New York City public schools that would result when layoffs are determined by seniority in comparison to a measure of teacher effectiveness. Due to data limitations and an interest in simplicity, this analysis employs the value added of teachers using the 4th and 5th grade math and ELA (English Language Arts) achievement of their students. Unsurprisingly, the authors find that layoffs determined by a measure of teacher effectiveness result in a more effective workforce than would be the case with seniority-based layoffs. However, they were surprised by facets of the empirical results. First, assuming readily available measures of teacher effectiveness actually measure true teacher effectiveness, an assumption to which they return in this brief, the differences between seniority and effectiveness-based layoffs are larger and more persistent than they anticipated. Second, even though seniority-based layoffs imply laying off more teachers, the differential effect on class size is very small in their simulations, though it would be larger for larger budget reductions. Third, there is a somewhat greater school-level concentration of layoffs in a seniority-based system, though with a few notable exceptions, both methods result in fairly dispersed layoffs, with the vast majority of schools having no more than one layoff in grades four and five combined. As a result of the limited applicability of teacher value-added measures to the full population of teachers as well as concerns about potential mismeasurement of effectiveness associated with using value-added measures even when available, neither seniority nor measures of value added to student achievement should be the sole criterion determining layoffs. However, ignoring effectiveness measures completely, as seniority-based systems do, is also problematic. Instead, the use of multiple measures of effectiveness for layoff decisions holds promise for softening the detrimental effect of layoffs. Teacher Value-Added Estimation is appended. (Contains 1 figure and 9 notes.)