To ensure unbiased samples, NCES statistical standards
require that participation rates for original school samples
be 70 percent or higher to report national results separately for public and private schools. In instances where participation rates meet the 70 percent criteria but fall below 85 percent, a nonresponse bias analysis is conducted.
Before substituting new schools for originally sampled schools that declined to participate, the weighted national school participation rates for the 2009 mathematics assessment were 97 percent for grade 4 (100 percent for public schools and 73 percent for private schools) and 97 percent for grade 8 (100 percent for public schools and 72 percent for private schools). Student participation rates were 95 percent at grade 4 and 93 percent at grade 8. The nonresponse bias analysis for private schools at grades 4 and 8 showed that substitution and weight adjustments reduced the potential bias.
Standards established by the National Assessment Governing Board require that school participation rates for the original state samples need to be at least 85 percent for results to be reported. In 2009, all 52 states and jurisdictions participating in the mathematics assessment at
grades 4 and 8 met this participation rate requirement.
The tables below provide participation rates before substitution.
Learn more about the sampling design.