When I was in middle school in US public school in the 90s, we had a Home Economics class where we were taught how to balance a checkbook, and that was about all the financial literacy that was covered.
Personally, I agree that it was a huge disservice to most students, and I think that a better general life skills class (I'd probably lump in civics/voting, dealing with various bureaucratic/administrative tasks, effective online research, personal privacy, how one might evaluate various professional services, resume writing etc) that includes basic financial literacy would be much more useful than just about anything else taught in school (to me, learning to socialize, properly empathize, and to reason and critically think are even more important, but also generally not part of most standard curricula).
After college, I got very into FIRE and personal investing, and eventually a while back put together my own basic financial literacy guide. It boiled down first to budgeting and calculating expenses (especially discretionary expenditures) vs earnings (As a school lesson, I think being forced to try to figure out a budget of a single parent on a minimum wage would be pretty eye-opening). For a general class, a practical lesson on tax filing would probably be worthwhile. And then for investing I agree about covering the general landscape of various savings and investments work, but more focused on in-depth/concrete lessons on fundamental concepts. Compounding, tax-advantage, dollar cost averaging, correlation, and rebalancing would basically cover it I think.
I think learning about how money (and debt) works - I'd argue that most people don't have a great understanding of that at all, some basic macroeconomics, and maybe some freakonomics type topics for color would be useful as well, but I don't think that financial literacy needs to go beyond the very basics to give everyone a bare minimum framework to be able do their own research/learning. But I also generally think that should be the goal of every topic taught, which seems to be rather at outs with mainstream teaching and learning practice in American public education.