Thank you for such a detailed comment. Maybe then I'm just missing the American context. Having lived in the UK and Australia (which have their own lion's share of education issues), to me it's obvious that students struggling should get support, and students who excel should be able to go further, and I don't think anyone imagines a system where everyone is always in one classroom with 100% the same learning.

I'm very against the idea that struggling students should just be "sacrificed" for the advanced student, however, which some of the other comments seem to be implying.