I'm not dumb per se, but I'm not great at reading dense material, so please try to help me out with sources that are accessible and digestible.
There wasn’t a uniform curriculum throughout the South, as different states and counties pursued their own policies – for example, authorizing particular history textbooks. In some places the teaching of civics and history was sharply restricted. For example, the county superintendent of schools in Mound Bayou, Mississippi, had apparently ordered that no American history between 1860 and 1875 – the period of the Civil War and Radical Reconstruction - be taught in the local public schools.
In 1964, a Freedom Summer volunteer wrote of Mississippi:
The students are taught nothing of their heritage. The only outstanding Negroes they are told about are Booker T. Washington and George Washington Carver. They learn nothing of the contributions Negroes have made to our culture or anything else which could give them any reason to disbelieve the lies they are told about Negroes being unable to do anything worthwhile.
On the other hand, there had been since the 1930s a countervailing movement led by Carter G. Woodson and others to promote the teaching of African-American history in black schools. Upset with the distorted image of African-Americans in standard histories, Woodson co-authored a 1935 high-school textbook titled The Story of the Negro Retold.
Woodson’s approach was roughly what we would describe today as “Afrocentrist”. His intent was counter anti-black stereotypes with an image of black agency and achievement: he described the ancient civilizations of Africa, placed a great deal of emphasis on slave resistance and revolts, as well as black participation in the abolitionist movement. His text includes a lot of material about slavery in Latin America and the British West Indies, providing an interesting comparative perspective.
Until the explosion of the African-American history texts in the 1960s, this would have been virtually the only high-school textbook that covered African-American history in a serious way. It would not have been assigned by state or county school boards, but instead would have been promoted by individual teachers, who would have become familiar with the Carter G. Woodson school of history at black colleges.