The Common Core of Data (CCD) public school file from which most of the sampled schools were drawn corresponds to the 2004-2005 school year, some 2 years prior to the assessment school year. During the intervening period, some of these schools either closed, no longer offered the grade of interest, or were ineligible for other reasons. In such cases, the sampled school was coded as ineligible.
Two jurisdictions to note are the eighth-grade samples for Louisiana and Delaware, where 20 to 25 percent of the schools were found to be ineligible. In these states, ninth-grade students in high schools who had not completed the requirements for eighth grade were counted as eighth-graders on the CCD, although these students were actually taking ninth-grade classes. Thus, many high schools sampled for the grade 8 assessment were later found to be ineligible.