Slowly working on a book I came across a while back (Lies My Teacher Told Me) that I knew going in was leftist propaganda, but it, and the usual moonbattery remind me that the left has no concept of how kids think and grow. They believe if you shove the "right" facts into those skulls full of mush, the kids, regardless of age, maturity, and ability just understand everything perfectly (the way the moonbats want them to think). You can't explain all the details of Columbus' journeys, interactions with the Native Americans he met (good and bad), his and other Europeans motives, ect to little kids. They cannot process all of it. But you have to start somewhere. From an admittedly eurocentric view, a good place to start is "Columbus discovered America" in grade school. As the kids mature, get more information, and develop more thinking skills (not that schools are working on those) we can introduce more details and more nuances, most of which would come in high school, some little bits in middle school.
That all applies to the Pilgrims, Thanksgiving, slavery in the Americas, the American Revolution, the Constitution, the Civil War, the Civil Rights movement, ect ect. But the proggies and moonbats don't care about any of that. The proggies just want good little indoctrinated, distracted worker bees and the moonbats just want to be indoctrinated so they don't have to be bothered with thinking on their own.