In Soviet Union algebra and geometry were taught from 5th to 11th grade to every kid in the country. And 10th & 11th grade algebra text-book was edited by Kolmogorov himself [0]. No surprise that _Russian School of Mathematics_ [1] after-school program is becoming very popular in the USA.

[0] Search for "algebra" in https://www.kolmogorov.com/Books.html

[1] https://www.russianschool.com/