At present, although the percentages of students with disabilities (SDs) and/or students who are English language learners (ELL) excluded from a NAEP administration are reported, no statistical adjustment is made for these excluded students in the calculation of NAEP results. However, the exclusion rates for both SD and ELL students vary substantially across jurisdictions at a given administration, and, in some cases, have changed substantially over time within a jurisdiction. Consequently, comparisons of performance based on reported NAEP scores may indeed be biased by differential exclusion and identification practices. Using only NAEP data, this report investigates plausible explanations for the observed heterogeneity among jurisdictions in exclusion rates.
