oh please they aren't having sex with the kid that sits at lunch by himself 
how does having access to girls his own age make him not want a teacher?
E
Actually in many cases it is. A few years back there was hot blonde, she specifically targeted a loner. As a matter of fact, she was married, and used the gifts that her husband gave her as a means of controlling the boy ("look what my husband gave me, you can't afford that.") And there are many of their examples said teachers picking the loner, or the one that "needs help".
Were you one of the cool kids? Because you seem like you can't pick up on these things?
It's not about not wanting the teacher, in many cases it's about the kid being the "prey". A popular kid who has access to women, has less time to deal with the teacher, and is not an easy target. Although, this is not always the case. Depending on the the looks of the teacher, and how immature that female teacher is (meaning the lack of separation between student and teacher) she may take this a way competing with the girlfriend for the
student's attention. There have been a few cases, where the girlfriend is the one who sounded the alarm.