Private schools represent about 23 percent of schools in the nation and educate about 9 percent of the students. In order to have a complete picture of the academic progress of the nation's students, selected students in public and nonpublic schools must participate in NAEP.
In the main NAEP assessments, the term "nonpublic schools" includes private schools as well as Bureau of Indian Education (BIE) schools and Department of Defense (DoD) domestic and overseas schools. Private schools can belong to religious organizations (of which the largest are Catholic schools), nonreligious organizations, or they can be independent schools. BIE and DoD schools are federally funded schools (that is, schools not supported by state or local governments). Private schools account for about 10 percent of the nation's students; BIE and DoD schools account for fewer than 1 percent of the nation's students. (Note that for the NAEP long-term trend assessments, BIE and DoD schools are selected for the sample only occasionally; when there is sampled a school in this category, it is reported in the long-term trend results in the "nonpublic" category with the private schools.).
NAEP selects samples representing the broad spectrum of nonpublic schools at grades 4, 8, and 12. Several different breakdowns by type of school are available, depending on assessment year and jurisdiction. (Note that Bureau of Indian Education schools and Department of Defense schools may be reported along with these nonpublic schools.)
Results for students in private schools are reported as a national average, but cannot be reported for states because the numbers of private school students asked to participate are too small to produce reliable results if reported by state. Several reports on private school performance are available in the Special Studies section of this website.
For each NAEP assessment, a sample of schools is selected from the Private School Universe Survey (PSS). The PSS collects and stores data on more than 33,000 nonpublic schools in the 50 states and the District of Columbia. The number of private schools sampled for NAEP changes from year to year depending on the assessment. However, the number of students per subject per grade typically remains the same—30 students in each school. Specific numbers of nonpublic schools and students that were both selected and that participated in past assessments can be found in the individual NAEP report cards for each subject or in a FAQ on the Nation's Report Card website, How many students participate? To ensure that the results reported for major student groups at the national level are accurate for private schools, oversampling (i.e., sampling particular types of schools at a higher rate than they appear in the population) is necessary.
Results for nonpublic schools can be examined through the NAEP Data Explorer (NDE). For each NAEP assessment, private school data are collected and included in the overall results. Private school results are also reported as a separate category in the years in which participation meets the NCES standard of at least 70% of schools in the sample. For most years, this is achieved; however, for some subjects, years, and grades, the symbol ‡ will show that the reporting standards were not met. Explore the Private School Quick Data tool to see a detailed look at results for private and public schools.
NAEP long-term trend (LTT) assessments give information on the changes in mathematics and reading performance of America's youth since the early 1970s. They are administered nationally every four years (but are not reported at the state or district levels) to students aged 9, 13, and 17.
NAEP assessment results make it possible to examine relationships between students' academic performance and the varied background information collected by NAEP. A relationship that exists between achievement and another variable, however, does not reveal its underlying cause, which may be influenced by a number of other variables. Simple or causal inferences related to, for example, student group membership, the effectiveness of public and nonpublic schools, and state- or district-level education systems cannot be drawn using NAEP results.