I suspect some in the HN community assume that because public school curriculums were generally so easy and aligned with textbooks such that they got all A's re

I suspect some in the HN community assume that because public school curriculums were generally so easy and aligned with textbooks such that they got all A's regardless of the teacher, that the teacher does not matter. No, the teacher definitely matters, as does the inflexible and oversimple curriculum and a million other factors. Switch 'teacher' with 'professor' and I highly doubt you would argue that quality no longer matters. The difference is that professors are less bound by stringent curriculums and teach more advanced material. This is where everyone really feels the difference. Whereas for public grade school teachers, an academically inclined student will only struggle under exceptionally bad teachers, less well academically inclined students will suffer without decent teachers even in grade school. The first quarter/semester at a good college typically provides a reality check for students who breezed through primary education.