One of the issues with teaching finance to kids is that is a) boring and b) not applicable for the kids who need it most. If you are a wealthy kid whose parents allocated you a big savings account or stock portfolio to "play with" in high school, that's one thing. If you're a poor kid just getting by, finance seems like "a rich person's playground".
I was the child of two immigrant parents. Growing up, we were always on the verge of bankruptcy as a family. Always about to miss a mortgage payment or a payment behind. Yet I grew up in a wealthy New York suburb so I was surrounded by a lot of kids described above, whose parents were overjoyed to teach their kids financial principles using inherited family wealth.
I got lucky in my own way. By the time I was 15 or so, I knew how to program a little, and was already an avid internet user (this, in the late 90s). Thus, I could do a little programming, and do web design projects for money.
So I started to build up savings, real cash savings, by the time I was 16. But then, it dawned on me: my parents weren't going to be able to afford sending me to college. So, I knew I had to build up savings in the few years leading up to freshman year to pay for college.
Then, I got into college (thankfully with a big scholarship) and dumped my savings into tuition and living expenses. I also continued working through college and took on student debt. By the time I was 19 or 20... I was very interested in finance. But I still operated entirely on a cash and debt basis. With $100K in loans, depressed savings, and parents entering retirement age with no savings other than the home equity they had in my childhood home. It's at that moment that some financial education would have helped me a whole lot.
I bring this up because I consider myself fortunate. People less fortunate than me never manage to build up any savings whatsoever in high school, and, if they are so fortunate to go to college, are drowning in way more debt and student loan payments than they can afford. By the time they enter the workforce, they are still digging themselves out of that debt, not yet thinking about the marvels of savings, capital investment, rate of return, and compounding interest. I worked for a couple years on Wall Street and made every mistake possible in this regard. I saved money in a 401k with crappy allocations that didn't perform well, leading into the 2008 financial crisis. I did an early withdrawal on that 401k to self-fund my startup. I operated on a cash & debt basis for years while earning sweat equity on that startup, and never diversified personally until very late.
I suspect for most young adults in a wealthy country, the moment when finance education would make the most impact is either senior year of high school or in college itself, or in the first year or two of work. If you teach it any earlier than that, it'll be in one ear, out the other.
When I used to work in Brooklyn, the local library held financial literacy courses targeted at young adults in NYC, scheduled for after work hours. I attended one and it was very well put together, and very well attended. I think that might be the best timing/setting of all for this.