"When I got an F on the first assignment in the new unit,
I had to give up trying. I knew that future assignments
and tests could only get more difficult."
I basically think that it is not necessarily connected
with the rest of the article, which is mostly about the
teacher being aggressive toward kids and not setting a
proper approach toward learning (yes, I had such teachers
during my schooling).
Many of my students who got an F at the beginning of the
new unit very soon earned a much better grade (such as a B
or an A) on the same material after they actually
concentrated on studying - that F woke them up. In one
case the school counselor started the intervention plan
after the HS freshman got Fs as most of his grades in the
first quarter.
I don't think that the sole purpose of an F is to
humiliate the student. If students did not know that their
knowledge and skills were insufficient, they would always
remain on that low level. We have the grading law that
states that "insufficient" or F is one of the five
possible grades. So basically if I give any grade but F to
a student whose skills and knowledge are insufficient, I
would be cheating.