@techreport{NBERw14265,
 title = "Selection Bias in College Admissions Test Scores",
 author = "Melissa Clark and Jesse Rothstein and Diane Whitmore Schanzenbach",
 institution = "National Bureau of Economic Research",
 type = "Working Paper",
 series = "Working Paper Series",
 number = "14265",
 year = "2008",
 month = "August",
 URL = "http://www.nber.org/papers/w14265",
 abstract = {Data from college admissions tests can provide a valuable measure of student achievement, but the non-representativeness of test-takers is an important concern. We examine selectivity bias in both state-level and school-level SAT and ACT averages.  The degree of selectivity may differ importantly across and within schools, and across and within states.  To identify within-state selectivity, we use a control function approach that conditions on scores from a representative test.  Estimates indicate strong selectivity of test-takers in "ACT states," where most college-bound students take the ACT, and much less selectivity in SAT states.  To identify within- and between-school selectivity, we take advantage of a policy reform in Illinois that made taking the ACT a graduation requirement.  Estimates based on this policy change indicate substantial positive selection into test participation both across and within schools.  Despite this, school-level averages of observed scores are extremely highly correlated with average latent scores, as across-school variation in sample selectivity is small relative to the underlying signal.  As a result, in most contexts the use of observed school mean test scores in place of latent means understates the degree of between-school variation in achievement but is otherwise unlikely to lead to misleading conclusions.},
}