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

February 2009

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.

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