The problem is that there are only so many hours in a school year and school career. All of Western Civilization is being crowded out in favor of kids digging worms and compost plus ethnic studies (where ethnic does NOT include “white”). Everybody is an ethnic except whites.
If they would get rid of all the crap that socialism has added to the curricula, there’d be plenty of time for all of American history, as well as a good sampling of world history. After all, they have twelve years in which to do it. Next to reading and writing, history is the most important subject to be taught. There’s only so much mathematics the average person needs. A good science foundation is important, but accurate history combines them all, and without it, not only do we not know our past, but will repeat its mistakes.