Mathematics and reading scores on the National Assessment of Educational Progress (NAEP) have increased among students attending elementary and secondary schools since the first time the assessment was administered. These score increases have been observed both for Black and White students; statistically significant score differences between the two racial/ethnic groups have also been observed. This statistical analysis report, "Achievement Gaps: How Black and White Students in Public Schools Perform in Mathematics and Reading on the National Assessment of Educational Progress," examines achievement gaps between Black and White public-school students at both the national and state levels. The report uses data from two assessment programs--main NAEP and Long-Term Trend (LTT) NAEP. While both programs assess reading and mathematics, they are different in three major respects: (1) main NAEP assesses performance of students in 4th- and 8th-grades, while LTT NAEP assesses performance of students ages 9 and 13; (2) main NAEP reports results for both the national and state levels, while LTT NAEP reports results for the national level only; (3) main NAEP was first administered in the 1990s, while LTT NAEP was first administered in the 1970s. The report uses results from all assessment years including the 2007 main NAEP and the 2004 LTT NAEP. All results are for public school students. The percentages of Black and White students in individual states vary by state. Some states' trends could not be reported because there were not enough Black or White students in the sample to have reportable results. This report is organized as follows. Following an introduction, the remainder of this report presents first mathematics and then reading results. In each section, long-term trend results are presented first, giving national results only for public school students ages 9 and 13. These are followed by both national and state results for public school fourth- and eighth-graders from main NAEP. National data from main NAEP are also presented by (1) gender; and (2) eligibility categories for the National School Lunch Program. The last section consists of two appendixes that contain relevant technical notes and supplemental tables. (Contains 12 footnotes, 11 tables, and 24 figures.) [This report was prepared under a project of the NAEP Education Statistics Services Institute (NAEP-ESSI) of the American Institutes for Research (AIR) in support of the National Center for Education Statistics (NCES). For the report highlights, see ED505902.]