Really opened my eyes.
German school was immensely frustrating to me. I'd lose grade for giving answers too early because the math level was so incredibly low.
At the same time I recognize now that in the grand scheme of things the average German high school is better than the average American one and that we had a lot things biology and chemistry that they don't seem to do until college
What evidence do you have of this?
If you're thinking of the PISA tests, Americans do well on PISA compared to their ethnic relatives. <https://www.unz.com/isteve/the-new-2018-pisa-school-test-sco...> Asian Americans do better than Asians; whites do better than Europeans; Latinos do better than Latin Americans; and blacks do better than Africans.
Hispanics and especially blacks' scores drag the US average down. Both white and Asian Americans score higher than Canada (and white+Asian is essentially Canada's racial makeup), and higher than New Zealand, Australia, the Netherlands, Belgium, Germany, France, Norway, and the UK; Estonia is below US Asians but above white Americans. Norway is by far the wealthiest Nordic state but its average is only two points higher than the US national average, despite not having a demographic that is 13% of the population and scores 85 points below the white American average.
Germany splits students into highschool (called Gymnasium, the academic track) and the vocational tracks at age 10.
Smart-kid highschool in Germany definitely moves faster than US highschools. Some even teach Greek and Latin for a well-rounded humanist education.
The US is an outlier among developed nations in terms of both numbers and composition for its minority population.
Example: The UK is 86% white. <https://en.wikipedia.org/wiki/Demography_of_the_United_Kingd...> Of the remainder, 7% are "Asian" (which in the UK almost always means Indian subcontinent, not east Asian as in the US) and 3% are black. By contrast, 13% of the US is black, and another 14-15% are Hispanic (of which about half are white). In other words, the percentage of the British population that is not white is about equal to the percentage of Americans that is black.
Plus, as I said, the huge gap in US PISA scores is between whites/Asians and blacks, not white and Asians. There are severe social dysfunctions among the Muslim portion of the British Asian population, but the non-Muslim portion performs very well on social and economic indicators.
Example: The largest Canadian non-white ethnicity is south Asian, at 7%, followed by Chinese at 5% and black at 4%. (Which is why I said that the ethnic composition of Canada is essentially white and Asian.)
It's a bit of an apples to oranges comparison between countries. Americans' concepts of equality and fairness are highly averse to the sort of separation-by-test-results that is core to the German secondary education system, so every school tries to cater to every type of student, with varied results.