This is an interesting complaint. I would argue that everyone whose knowledge of history consists of the entirety of their high school curriculum, with nothing forgotten, is shockingly ignorant of history.

After reading one relatively short book on the history of China, ( https://www.amazon.com/dp/0465015808/ ), I had a Chinese high school student remark to me on how unusual it was for her to find someone who could talk about Chinese history. But I was meeting only the lowest possible bar.

If someone is shockingly ignorant of history, that's not because they missed high school; it's a problem that high school doesn't try to address and isn't intended to.