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

Value-added measures of teacher quality may be sensitive to the quantitative properties of the testing instruments upon which they are based. This paper focuses on the sensitivity of value-added to a particularly relevant testing-instrument property test-score-ceiling effects. Test-score ceilings are likely to be 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.