History majors at top colleges don’t know much about U.S. history—or at least they don’t have to.

A new report by the American Council of Trustees and Alumni, a nonprofit group that advocates for accountability at schools, found that just 23 of the institutions among the 76 deemed to be the “best” by U.S. News & World Report’s 2016 rankings require history majors to take at least one U.S. history course.

Many elite schools, including Rice University and Johns Hopkins University, may require students to take courses about events from before 1750, or on East Asian and sub-Saharan African politics, without also demanding that they study the creation of the U.S. Constitution or the civil-rights movement.