Teacher is a virgin until 40, and gets magic powers: specifically the power to have his activities ignored when he's naked, and the ability to make people go along with whatever he's doing. Uses his power to get revenge on all the kids who treated him shitty 10 years ago in his class. Especially targeting one girl who's now an expectant mother.
This is actually a 2-for-1, with a second shorter story on the end about the day he awoke to his powers.