What It's Like When You Have to Give a Student an "F"

Just as no student likes to see an F on her report card, it's not exactly easy for teachers to give them, either. "A few days before the end of the marking period, a couple of students will rescue themselves, not with extra credit, but making up their assignments. I’ll be nice and accept them for some credit. But the others who need it the most won’t get the hint, even after I make it plain for them."

Since a teacher can't give a D when a student has earned an F, what happens moving forward?