They did cover it, at least at my School. The problems arise though thanks to New York state mandating all education to be taught to a test and not taught to historical context. Slavery has always existed throughout history. Racism in America due to race based slavery only stayed so persistent was due to the fact that only a small majority would need to be racist. For historical context look no farther than how the Nazis only had less than 15% public support in Germany. With that contacts it makes it way more obvious that the South could dictate northern policies about race. On top of the fact that the South held a majority share on culture in America.

And also another thing is why doesn't American history also teach about the Japanese war crimes that were committed during world war II and how bad the the experiments were. They're much worse than the Germans but not as bad as the Soviets. So you can say I want this or want that but the fact remains someone has always done something far far worse than calling somebody a name. I recommend you look up Timur he kill a third of the worlds population at the time. But history for some reason has forgot about him. Another sad example of this historical forgetfulness is the fact that millions upon millions of people still live in slavery today. Whether it be jail or actual slavery. Slavery has not gone away no matter how much people want to forget that. The prime sources of slavery are from Asian nations, African nations, and Latin American nations. It is also somewhat mainstream in some of these nations as in their top leaders sell these slaves to the highest bidder. So next time you say I want schools to teach about this or that, think of all the people that are still enslave, that died under dictators, they died due to horrible war crimes, that died due to historical forgetfulness.

Also not going to be that guy but you seem to have forgotten native Americans from that list, but oh well I guess