@techreport{NBERw14778,
 title = "Value-Added to What?  How a Ceiling in the Testing Instrument Influences Value-Added Estimation",
 author = "Cory Koedel and Julian Betts",
 institution = "National Bureau of Economic Research",
 type = "Working Paper",
 series = "Working Paper Series",
 number = "14778",
 year = "2009",
 month = "March",
 URL = "http://www.nber.org/papers/w14778",
 abstract = {Value-added measures of teacher quality may be sensitive to the quantitative properties of the student tests upon which they are based.  This paper 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.},
}