The proper level of education doesn't really mean college education - having 100% people go from high school to college isn't a goal, shouldn't be a goal and is not a desirable thing in any way whatsoever. For many "life paths" that any society needs going to college is a good thing, and for many of them it's a bad thing, wasting many years. This education should be available for the people who choose it, and people shouldn't be excluded for
economic reasons; but for many people foregoing this choice wouldn't be a "wasted opportunity" but a good thing.
If anything, the USA education system has a problem with "overeducation" and not undereducation, mainly because weakness of vocational studies causes people to spend many extra years for gaining skills that could have been gained in a much shorter and efficient vocational study program.
It's not a problem for wealthy kids who can afford to spend a few years on the parts of the "college experience" that (in some cases) is less like investment in skills but more like a fancy self-improvement hobby, but we harm the poorer people if we make the education path unnecessarily long and thus expensive; it may make gaining the proper skills unaffordable even if education itself would be free, simply because they can't afford to waste this time without income before starting full time work.