Reverse psychology does the trick
If you’re on the verge of an A-, what would you do? Many of us would probably take the B+ and smile. But one person had more to fear than bad grades. If their parents found out that they were on the cusp of an A-, there would be hell to pay.
So, this student, perhaps very cleverly, asked the professor to lower their grade. Perhaps if they were more than a point shy of a better grade, mom and dad would understand that their child’s best was pretty far from the victory line. What the professor decided to do instead was raise the grade to an A-. Reverse psychology at its finest, folks.