SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), various years, 1990–2007 Mathematics Assessments.
To read more details related to students' responses to background questions about parental education levels, see NAEP Reporting Groups.
To read more about achievement levels and how they are set, see Reporting the Assessment—Scale Scores and Achievement Levels.