​​​​​​​​​​​NAEP Technical DocumentationSchool Sample Selection for the 2024 Twelfth-Grade Private School National Assessment

The sampled schools for the twelfth-grade private school national assessments in mathematics and reading came from two frames: the primary private school sample frame constructed from the ​​Private School Universe Survey (PSS)​ file and the supplemental new-school sampli​ng frame. Schools were sampled from each school frame with probability proportional-to-size (PPS) using systematic sampling. Prior to sampling, schools in each frame were sorted by the appropriate implicit stratification variables in a serpentine order within each explicit sampling stratum. (For details on explicit and implicit strata used for these samples see the stratification page.) A school's measure of size was a complex function of the school's estimated grade enrollment. Only one hit was allowed for each school.

Schools from the PSS-based frame were sampled at a rate that would yield a national sample of 5,000 assessed students (2,500 each from the Catholic and non-Catholic school strata). Catholic schools from the new-school frames were sampled at the same rate as those from the PSS-based frame.

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