In university students often spend time in large lectures in math classes. There's no real to expect that to be a lot more effective than a 15 person course with a good teacher.

I just assumed based on my own experience that the schools themselves wouldn't be good enough to support this, or wouldn't be incentivized correctly.

In our times the incentives go against teaching like this. in Berlin centralized math testing effectively means that all schools have to teach to the same test and that test doesn't contain complicated proofs.

I now recall that my father, who went to high school in Kiev in the 70s, used to tell me that the math I learned in the freshman year, they learned in high school.

Yes, the difference between a math education at bad school with only 3 hours per week at the end and the math education at a good school in Germany with 5 hours per week might be the freshman year of a non-CS math content of a CS undergrad degree.