I should have realized this, since my kids went to a French immersion school, but math (and science I think) is different in the US than many other places. For some reason, in the US educators treat math and science as if there are neat, distinct subareas which do not depend upon or intertwine with other subareas. Algebra I is distinct from Geometry and Algebra II, Biology has nothing to do with Chemistry, etc. After seeing the European way of teaching math and science, my kids think the US way is stupid since we know these subareas cannot be used in isolation.
By the end of HS, the US kids may have covered the same math and science as their European counterparts, but if you look at things prior to then, the US kids may cover some topics earlier while the European kids cover other topics earlier.
I think my kids bisected a line around third grade, but that was at the French school. Didn't get back to that until 8th grade in the US public school.
