Value Added to What? How a Ceiling in the Testing Instrument Influences Value-Added Estimation

Abstract

Value-added measures of teacher quality may be sensitive to the quantitative properties of the student tests upon which they are based. This article focuses on the sensitivity of value added to test score ceiling effects. Test score ceilings are increasingly common in testing instruments across the country as education policy continues to emphasize proficiency-based reform. Encouragingly, we show that over a wide range of test score ceiling severity, teachers' value-added estimates are only negligibly influenced by ceiling effects. However, as ceiling conditions approach those found in minimum-competency testing environments, value-added results are significantly altered. We suggest a simple statistical check for ceiling effects.