* See this indicator’s supporting table for information as to which year-to-year changes are statistically significant.
** Data for years 2004 and later are based on a revised assessment. See https://nces.ed.gov/nationsreportcard/ltt/howdevelop.aspx for an overview of the differences between the original and revised assessments.
Source: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, The Nation’s Report Card: Trends in Academic Progress 2012, NCES 2012-456 (Washington, DC: U.S. Government Printing Office, 2012), 15 fig. 6.