Is it normal my boyfriend claims he is not infatuated with a hot woman anymore?

My boyfriend is a school teacher. At the beginning of every school year, he develops crushes on new women at the school (not students). At the beginning of the year, there is always an influx of new women on staff.

Now there is a teacher's aide that is in an exercise class with him. He has admitted he would like to have sex with her, and watches her dance around during the class.

Now he says he has seen who she is, and he is not attracted to her anymore. Is it possible to lose attraction for someone this quickly (2 months). He says she is too jock like. But he was really into her!