Val, perhaps I am overstating the point a bit. Of course, there are differences between good and bad instruction. Otherwise, we wouldn't need teachers of any kind. But my (possibly exaggerated) point is simply that beyond a minimum level of instructional quality, much of the difference in educational outcomes is reflective of the extracurricular resources of the individual student (prior learning, family resources, experiences, study skills, motivation, etc.). For most of the respectable range of four-year colleges, it seems to me that the effort, expense, and anxiety invested by a middle-class-plus family into attempting to move their child's college admissions up a tier is disproportionate to the educational gains resulting.

...pronounced like the long vowel and first letter of the alphabet...