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Scale Scores and Achievement Levels

The National Assessment of Educational Progress (NAEP) presents assessment results of student performance in two ways: 

  • average scores on the NAEP subject scale, and
  • percentages of students attaining NAEP achievement levels.

Scale Scores

NAEP assessment results are reported as average scores on a 0-500 scale (reading, mathematics, U.S. history, and geography) or on a 0 -300 scale (science, writing, and civics). These scale scores, derived from student responses to assessment questions, summarize the overall level of performance attained by that student. Scale scores for individual students are not reported, but summary statistics describing scale scores for groups of students (demographic, gender, race/ethnicity, etc.) are reported.

Scale scores can be used for comparisons between the nation, states, and selected districts, as well as among student groups (e.g., Black/White, Hispanic/White). Because NAEP scores are developed independently for each subject, results cannot be compared across subjects.

See short descriptions of scale scores for each assessment subject:

NAEP Achievement Levels

Achievement levels are performance standards that describe what students should know and be able to do. Results are reported as percentages of students performing at or above three achievement levels (Basic, Proficient, and Advanced). Students performing at or above the Proficient level on NAEP assessments demonstrate solid academic performance and competency over challenging subject matter. It should be noted that the NAEP Proficient achievement level does not represent grade level proficiency as determined by other assessment standards (e.g., state or district assessments). See short descriptions of achievement levels for each assessment subject:

setachlevelsSetting of Achievement Levels

NAEP achievement levels are set by the National Assessment Governing Board based on the collective judgments of a broadly representative panel of teachers, education specialists, and members of the general public. The authorizing legislation for the National Assessment of Educational Progress (NAEP) requires that the achievement levels be used on a trial basis until the Commissioner of the National Center for Education Statistics (NCES) determines that the achievement levels are reasonable, valid, and informative to the public (20 USC § 9622(e)(2)(C)). The NCES Commissioner’s determination is to be based on a congressionally mandated, rigorous, and independent evaluation. The latest evaluation of the achievement levels was conducted by a committee convened by the National Academies of Sciences, Engineering, and Medicine in 2016. The evaluation concluded that further evidence should be gathered to determine whether the achievement levels are reasonable, valid, and informative. Accordingly, the NCES commissioner determined that the trial status of the achievement levels should be maintained at this time.

Interpreting Scale Scores and Achievement Levels

NAEP reports results using widely accepted statistical standards; findings are reported based on a statistical significance level set at 0.05, with appropriate adjustments for multiple comparisons. Only differences found to be statistically significant are referred to as higher or lower.

Comparisons over time of scores and percentages or among groups are based on statistical tests that consider both the size of the difference and the standard errors of the two statistics being compared. Standard errors and estimates based on smaller groups are likely to have larger margins of error. For example, a 2-point change in the average score for the nation may be statistically significant, while a 2-point score change for a state is not due to the size of the standard errors for the score estimate. The size of the standard errors may also be influenced by other factors, such as the degree to which the assessed students are representative of the entire population.

A scale score that is significantly higher or lower in comparison to an earlier assessment year is reliable evidence that student performance has changed. NAEP is not, however, designed to identify the causes of change in student performance. Although comparisons are made in students’ performance based on demographic characteristics and educational experiences, the comparisons cannot be used to establish a cause-and-effect relationship between the characteristic or experience and achievement. Many factors may influence student achievement including educational policies and practices, available resources, and the demographic characteristics of the student body. Such factors may change over time and vary among student groups.

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Last updated 14 May 2018 (JA)