Engineering Curve
Due to the inevitable sausage fest that is an engineering classroom, the few girls in the class are considered hotter than they typically are on a 10 point scale while the guys s appear uglier than they are. i.e. a girl's hotness rating rises as the girl/guy ratio gets worse.
The only girl in the class is a 2, but due to the engineering curve she's a 5 because we're all horny dudes.