Within any assessment year, exclusion and accommodation rates may vary across jurisdictions. In addition, exclusion and accommodation rates may increase or decrease between assessment administrations, making it difficult to interpret comparisons over time within jurisdictions. Since students with disabilities (SD) and English language learners (ELL) tend to score below average on assessments, exclusion of students from these groups may result in a higher average score than if those students had taken the assessment. Providing appropriate testing accommodations (e.g., providing extended time for some SD or ELL students to take the assessment), on the other hand, removes barriers that would otherwise prevent them from demonstrating their knowledge and skills.
NCES has commissioned several studies of the impact of exclusion and accommodation rates on overall scores. NCES has also investigated scenarios for estimating what the average scores might have been if excluded students had been assessed. The data in the sections below are presented as an exploration of how accommodations and exclusion rates may impact assessment results for jurisdictions that participated in the NAEP assessments.
NCES conducted research to develop a methodology for measuring state and urban district inclusion rates while taking into account the differing demographics and policies in each participating jurisdiction. The research provided a methodology and two measures of change in each participating jurisdiction's inclusion rate taking into consideration the following factors that differ across jurisdictions and time:
Two sets of results are available from that research which compared data from the 2005 and 2007 reading and mathematics assessments at fourth and eighth grade.
One way to investigate the potential impact of accommodation rates is to examine the results for the subset of the population that was not given testing accommodations. Students who were not accommodated include students who may or may not have been identified as SD and/or ELL. Another way to examine the potential effect of accommodation rates is to view performance data for only those students who were not identified as SD and/or ELL. Comparing the results reported for all assessed students to those for nonaccommodated or non-SD/ELL students provides some indication of the impact of the accommodations. The tables below provide such estimates for the urban districts that participated in the 2007 Trial Urban District Assessments in mathematics, reading, and writing. In the mathematics and reading assessments where previous assessments were administered in 2005, the trends in performance were the same in most districts for all students, for nonaccommodated students, and for non-SD/ELL students. This suggests that provision of accommodations did not affect the mathematics or reading trends for these districts.