A good, free education is to the benefit of society.

You do not incur a debt for the 12 years of school you're already mandated to receive, because that education makes society better. You become a better, more productive adult as a result of it.

But now we find that that education is not enough. Most people are not graduating high school with the necessary skills and knowledge to become that fully functioning adult. So, it is too society's benefit to extend that education.

This should not be transactional. We the people provide the education, and we the people benefit.

Otoh, there's always work digging ditches or nursing. Most people would prefer nursing in that scenario. Extend this metaphor to whatever job we're short of and make that education free until we're not short of it anymore.

Once they do, you’d owe them. Maybe not dollars, maybe a moral obligation, but they’d only give you something expecting a return

Most advanced countries will give you all of your formal education for free or with a heavily subsidized cost.

It usually don't create an obligation, or some kind of moral one. Managers have this joke (that for some reason they never think about) where they are deciding of they'll train their employees, and one asks "what if we train them and they leave?", so the other respond "what if we don't train them and they don't?". State payed education is just that, but at a society level, and for everything the society expects from people instead of just work.

expecting a return

It's called taxes. In many normal places, some people qualify (based on secondary education grades or other things like military service) to receive free higher education (basically sponsored by the government) that is paid off later over the years by taxes or contributions to the GDP.

Fuck that, I never asked to be born. Send the bill to my parents.

I guess I take issue with the fact that you can't realistically opt out. Maybe if you are a wilderness survivalist type then maybe you can go do a Thoreau or Davy Crocket or whatever and just build a log cabin in the woods somewhere. But that's very rare these days, and society is moving forward so fast that tens of millions of people are being left behind because they lack the technical skills to thrive in a modern economy, and the survival skills to thrive in an old school agrarian economy. When that many people are left behind, it becomes a major social problem that'll come home to roost eventually.

Ah no, educated citizens is to the advantage of the society. Not in working power but in not falling back to a totalist system with low living standards.