NAEP Technical DocumentationSampling Frame for the 2008 Private School Long-Term Trend (LTT) Assessment

The frame of the private schools was developed from the 2003-04 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 2003-04 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 area.

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, home-school entities, prison and hospital schools, virtual and online 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 school count 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 frame, long-term trend (LTT) assessment, by affiliation and age: 2008
Age	Affiliation	School count in sampled primary sampling units (PSUs)	Estimated enrollment (unweighted)	Estimated enrollment(weighted)
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008 Long-Term Trend Assessment.
9	Total	10,602	212,987	391,433
	Catholic	3,155	103,814	186,307
	Non-Catholic	6,406	103,968	194,976
	Unknown affiliation	1,041	5,205	10,150
13	Total	10,879	206,267	381,801
	Catholic	3,682	103,798	186,378
	Non-Catholic	6,156	97,264	185,273
	Unknown affiliation	1,041	5,205	10,150
17	Total	4,685	167,983	294,180
	Catholic	641	91,340	150,499
	Non-Catholic	3,003	71,438	133,531
	Unknown affiliation	1,041	5,205	10,150

For quality control purposes, school and student counts from the sampling frame were compared to school and student counts from the LTT 2004 private school frames. No major discrepancies were found.

Last updated 12 January 2011 (JL)

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