Yeah, the one where freshman physics in college blew threw 2 years of daily honors public school physics in 2 weeks. The one where the high school diploma is nigh worthless in the marketplace. The one where the students have no skin in the game and disrupt the classes and assault the teachers.
It all does not have to be free, just a government funded option to provide a floor. Public school was my only saving grace, being from an immigrant family that did not know English or how to navigate America.
Although, I also do not think government needs to pay for free schooling for 17 years. Can easily cut some fluff and drop that to 15 years, and still give people a solid foundation equivalent to a Bachelors.
The issue is the pareto principle. As it is the CSU/UC systems cannot support every applicant that wants to come in. But making it completely free they'd be flooded with most of the country's prospective students.
Also, schools are state funded as well as federally funded. So there's a bunch of issues when it comes to out of state students and who should cover. That exists even with today's crazily high priced tuition.
In most cases higher education is to some extent "rationed" and generally less accessible than in the US. Only a few countries in Europe have more University graduates. Which is of course perfectly rational if you have no ideological objects to some degree of centralized planning.
Oxford (like Harvard) is often less about what you'll know and more about WHO you'll know.
At the undergrad level, the subject matter is generally very well-established. But when you want a job after graduation, being close friends with the CEO's child helps far more than a few tenths of a point on your GPA.
Legacy admissions and nepotism are still very much a thing.
Just make the schools free for all, and collect with higher marginal income / wealth taxes.
It should not be dependent on parents’ status either. I got zero aid due to my parents, but I also got zero from my parents.