'Good' students learn well by sitting in a large lecture and doing homework. Getting a number back on a homework assignment is sufficient feedback for students to learn from their mistakes. Every student's knowledge is equally evaluatable by exams. Student success in a class can be meaningfully categorized into a single letter grade. Students all have the appropriate prerequisite knowledge and remember it well. Students can all grasp the material at about the same rate, and certainly within one semester. Students feel comfortable talking one on one to professors or TAs during office hours.

Certainly this works well enough for many students. But it absolutely does not work for many others who are otherwise bright, capable individuals. Some people have extenuating personal circumstances — family that need support, relationship troubles, kids, poverty. An increasing number of people have anxiety problems. A lot of people have not had a good pre-college education to draw on and struggle to make that up whilst 'good' students get better grades because they had a better upbringing.

I think some of the best learning I've done is sitting down with a friend or two and a book and working through it at our own pace until we're satisfied we know what's going on. No exams, no answer key — we do the exercises and discuss our approaches until we agree on what 'the' answer is.