Here's my theory: attractive math teacher was a wanna be popular chick or unpopular geek in high school.
So, she loses some weight, fills out, dresses seductively, offers extra credit to the jocks who need most help and have the "popular" status to redefine her existence.
Outside of bull movies, how many hot chicks were good at math? How many popular chicks were good at math? How many fun chicks were interested in algebra, trig, calculus? That's what this chick is teaching if she's teaching 17-18 year olds.
So, she wasn't popular or liked and now she is. Or was. In jail she will be again!