Approximately 74 percent of fourth-graders had teachers who reported covering the historical period before 1815, while 42 percent of students had teachers who did not cover the period from 1945 to the present.

NOTE: Detail may not sum to totals because of rounding. Some apparent differences between estimates may not be statistically significant. See complete data for the following time periods: Before 1815
, 1815 to 1865
, 1865 to 1945
, 1945 to present
.
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2010 U.S. History Assessment.