Alabama, Florida and New York require teaching not only about Dr. King but also about others like James Meredith, who in 1962 became the first black student to enroll at the University of Mississippi; Medgar Evers, the rights organizer murdered the following year in Jackson, Miss.; and Malcolm X, the Muslim minister who challenged the movement’s predominantly integrationist goals.

Some experts in history education criticized the report’s methodology. Fritz Fischer, a professor at the University of Northern Colorado who is chairman of the National Council for History Education, said it was unfair to give Colorado and some other states an F because of vague state history standards, when they are required by state constitutions or laws to leave curriculum up to local districts.

“The grading system they came up with does a disservice in putting the focus on requirements that certain states are unable to meet and will never be able to meet,” Dr. Fischer said.

Even though Colorado’s standards barely mention the civil rights movement, some Colorado schools teach the civil rights movement thoroughly, he said. “I’ve been in classrooms and watched them teach about the sit-ins and about the controversies between Martin Luther King and Malcolm,” he said.

The report is by no means the first to sound an alarm about nationwide weaknesses in the teaching of American history.

Over the past decade, students have performed worse on federal history tests administered by the Department of Education than on tests in any other subject. On the history test last year, only 12 percent of high school seniors showed proficiency.

The law center’s report noted that on that federal test, the National Assessment of Educational Progress, seniors were asked to read a brief excerpt from the Supreme Court’s 1954 Brown v. Board of Education ruling, including the phrase, “Separate educational facilities are inherently unequal.” Only 2 percent of the seniors were able to state that the ruling had been prompted by a school segregation case.