​​​​​​​​​NAEP Technical Documentation Sampling Frame for the 2022 Private School Long-Term Trend Assessment

			Age Distribution Fractions New-School Sampling Frame

The primary sampling frame for private schools was developed from the Private School Universe Survey (PSS) corresponding to the 2019–2020 school year. The PSS file is the Department of Education’s primary database of elementary and secondary private schools in the 50 states and the District of Columbia, and it is based on a survey conducted by the U.S. Census Bureau during the 2019–2020 school year. This sampling frame is referred to as the PSS-based sampling frame.

The PSS-based sampling frame was restricted to schools located in the primary sampling units (PSUs) selected for the NAEP 2022 long-term trend (LTT) assessment. In addition, the sampling frame excluded ungraded schools, vocational schools with no enrollment, special-education-only schools, homeschool entities, prison and hospital schools, and juvenile correctional institutions. Vocational schools with no enrollment serve students who split their time between the vocational school and their home school.

The following table presents the number of schools and estimated enrollment for the PSS-based sampling frame by age population​. The unweighted estimated enrollment is restricted to the selected PSUs. The weighted estimated enrollment incorporates the PSU weight (inverse of the probability of selecting the PSU) and the estimated age-eligible enrollment, and thus is a national estimate of the number of private school students in the age population​. The age-eligible enrollment was estimated using age distribution fractions (see link above right) derived by grade for each age population.

For quality control purposes, school and student counts from the sampling frame were compared to school and student counts from previous private school frames by grade (for grades 4 and 8). Comparisons were grade-based because most NAEP assessments are grade-based, and grade counts are a reasonable proxy for age counts for comparison purposes. No major discrepancies were found.

A secondary sampling frame was also created for the age 9 sample to account for schools that newly opened or became newly eligible between the 2019–2020 and 2021–​2022 school years. This frame contains brand-new and newly-eligible schools expected to have 9 year olds and is referred to as the new-school sampling frame. Because there are no sources available to identify new schools for non-Catholic private schools, the new school frame for private schools contains only Catholic schools. Like the PSS-based frame, the new-school sampling frame was restricted to schools in the selected PSUs and certain types of schools were excluded from the frame as described above.

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