NAEP Technical DocumentationSampling Frame for the 2012 Private School Long-Term Trend (LTT) Assessment

The sampling frame for private schools was developed from the 2009-2010 Private School Universe Survey (PSS), a survey conducted by the U.S. Census Bureau for the National Center for Education Statistics (NCES). The PSS is a biennial mail survey of all private schools in the 50 states and the District of Columbia. The PSS frame of schools comprises both a list frame and an area frame. The list frame is an assembly of the 2007-2008 PSS frame and more up-to-date lists from state education agencies, private school associations, and other easily accessible sources. To improve the coverage of the PSS list frame, the Census Bureau also conducted a survey to locate private schools in a random sample of geographic areas throughout the United States. The areas were single counties or groups of counties sampled from an area frame constructed from all counties in the nation. Within each selected area, a complete list of private schools was gathered using information from telephone directories, religious institutions, local education agencies, chambers of commerce, and local government offices. Schools not already on the list frame were identified and added to the frame of private schools. A weighting component was computed by the Census Bureau so that the additional area-frame schools would represent all schools absent from the list frame, not just those in the selected areas.

The sampling frame was restricted to schools located in the primary sampling units (PSUs) selected for the 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.

The following table presents the number of schools and estimated enrollment for the private school 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 derived for each grade in the age range.

Number of schools and enrollment in private school sampling frame, long-term trend (LTT) assessment, by affiliation and age: 2012
Age	Affiliation	Number of schools	Estimated enrollment (unweighted)	Estimated enrollment (weighted)
NOTE: Detail may not sum to totals because of rounding. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2012 Long-Term Trend Assessment.
9	Total	9,500	191,000	361,000
	Catholic	2,800	83,600	150,000
	Non-Catholic	6,400	105,000	206,000
	Unknown affiliation	360	1,700	4,100
13	Total	10,000	188,000	357,000
	Catholic	3,300	86,700	153,000
	Non-Catholic	6,300	99,100	200,000
	Unknown affiliation	360	1,700	4,100
17	Total	4,400	181,000	334,000
	Catholic	669	92,100	150,000
	Non-Catholic	3,300	86,800	181,000
	Unknown affiliation	360	1,800	4,100

For quality control purposes, school and student counts from the sampling frame were compared to school and student counts from the LTT 2008 private school frames. No major discrepancies were found.

Last updated 26 February 2016 (GF)

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