About the NAEP Long-Term Trend Assessment
The National Assessment of Educational Progress (NAEP) has monitored student performance since the early 1970s through its long-term trend (LTT) assessments. Results from the 2020 LTT assessments in reading and mathematics are based on nationally representative samples of 9- and 13-year-olds. Since its beginning in 1969, the primary mission of NAEP has been to measure academic progress by regularly administering various subject-area assessments to nationally representative samples of students. The existence of two national assessment programs—LTT and main NAEP—makes it possible to meet two major objectives: (1) to measure students' educational progress over a long period of time (LTT), and (2) to measure students' knowledge and skills based on the most current curricula and standards (main NAEP). It should be noted that results from the LTT assessments cannot be directly compared to those from the main NAEP assessments because the LTT assessments use different questions and because students are sampled by age rather than by grade. Learn more about the differences between the LTT and main NAEP assessments.
Several changes were made to the LTT assessment in 2004 to align it with current assessment practices and policies applicable to the main NAEP assessments. A bridge study was conducted to ensure that the trend line could be continued over time. The 2004 bridge study involves administering two assessments: one that replicates the assessment given in the 1999 and prior assessments (a bridge assessment or the original assessment format), and one that represents the new design (a modified assessment or the revised assessment format). Results for 1971–99 presented in this report are from the original assessment format, and results for 2004–20 are from the revised assessment format. In addition, results for both the original and revised assessment formats are presented for the 2004 LTT assessment. Read more information about the two assessment formats and changes made to the LTT assessment.
Samples, Inclusion, and Participation
The target population for the 2020 NAEP long-term trend assessments consisted of 9- and 13-year-old students enrolled in public and private schools nationwide. Eligibility for the age 9 and age 13 samples was based on the calendar year. Students in the age 9 sample were 9 years old on January 1, 2020, with birth months January through December 2010. Students in the age 13 sample were 13 years old on January 1, 2020, with birth months January through December 2006. The national samples for students at ages 9 and 13 were chosen using a multistage design that involved drawing students from the sampled public and private schools across the country. Within each age group, the results from the assessed students were combined to provide accurate estimates of the overall performance of students in the nation.
The schools and students participating in NAEP assessments are selected to be representative of all schools nationally. The results from the 2020 LTT reading assessment at ages 9 and 13 are based on the 8,400 nine-year-olds from a nationally representative sample of 8,700 age 9 students and the 8,900 thirteen-year-olds from a nationally representative sample of 9,100 age 13 students. The results from the LTT mathematics assessment at ages 9 and 13 are based on the 8,400 nine-year-olds from a nationally representative sample of 8,600 age 9 students and the 8,900 thirteen-year-olds from a nationally representative sample of 9,100 age 13 students. The long-term trend assessments are not designed to provide results for individual states or large urban districts. Results are reported for the nation only.
Number of participating schools and students in NAEP long-term trend reading and mathematics assessments, by student age group: 2020
Each school that participated in the assessment and each student assessed represents only a portion of the larger population of interest. The results are weighted to account for the disproportionate representation of some groups in the selected sample, including oversampling of schools with high concentrations of students from certain racial/ethnic groups and the lower sampling rates of students who attend small schools. Read more about NAEP sampling and weighting in the NAEP Technical Documentation.
School and Student Participation
The weighted national school participation rates (before replacing originally sampled schools that declined to participate with substitute schools) for the 2020 long-term trend assessments are presented in the table below. Although not shown in the table, national student participation rates for 9-year-old students were 94 percent in reading and 93 percent in mathematics, and national student participation rates for 13-year-old students were 93 percent in reading and 92 percent in mathematics. Please see the appendix table for the weighted school participation rates after substitution and the details for the student participation rates.
School participation rates in NAEP long-term trend reading and mathematics assessments, by student age group and type of school: 2020
|Type of school||Age 9||Age 13|
To ensure unbiased samples, NAEP statistical standards require that participation rates for original school samples be 70 percent or higher to report national results separately for public and private school students. At both ages, the school participation rates met the standards for reporting results separately for public schools in 2020 but not for private schools. Catholic school participation rates, however, did meet the standards in 2020 for reporting results separately; therefore, results for Catholic schools are included in this report.
Assessing representative samples of students, including students with disabilities (SD) and English learners (EL), helps to ensure that NAEP results accurately reflect the educational performance of all students in the target population and are a meaningful measure of U.S. students' academic achievement over time.
To ensure that all selected students from the population can be assessed, many of the same accommodations that SD and EL students use on other tests are provided for those students participating in NAEP. Prior to 2004, no testing accommodations were allowed for students identified as SD and/or EL selected to participate in the long-term trend assessments. One of the changes introduced as part of the 2004 assessments was the use of accommodations, such as extra testing time or individual rather than group administration for students who needed such accommodations to participate in the assessments. The results for the 2004, 2008, 2012, and 2020 long-term trend assessments are based on administration procedures that also allowed accommodations.
Information on exclusion rates of SD and/or EL students was first collected in 1990. At that time, about 5 to 6 percent of all students at each age group were excluded from the long-term trend assessments. By 2020, about 2 percent of all students at each age group were excluded.