A student who has learned nothing will not receive an F because the professor doesn't want to admit that his teaching hasn't been compelling and/or effective.
That's not true. Professors would love to fail more students. But if you do, then you tons and tons of complaints, the university gets on your ass, and then you have to go back and change a few Fs to Ds. It's not worth the headache.
The biggest lesson I have learned was that if you fail people, you should make sure that those who fail correctly reflects the demographics (e.g. black people, women). Otherwise it is a fuck-up with some very nasty complaints.
And the problem is that at the university I teach at, being an ethnic minority is worth 20 pts of the 100 pts necessary for admission; the same number of points as a full grade point average. That means that the black students did a full grade point worse in high school, on average, than the white students they're competing with. I fudge this by grading my black students easier than my white students on essays/exams.
(based on the assumption that they score the same in other areas. That assumption is obviously not true, but the other areas where they might differ have such small point values it's close enough.)
That's not true. Professors would love to fail more students. But if you do, then you tons and tons of complaints, the university gets on your ass, and then you have to go back and change a few Fs to Ds. It's not worth the headache.