They were a lot less slutty back then, and knew better than to cross certain lines even if they were slutty. This is NOT the same culture I grew up in...
A long time ago a 24 year-old was an adult. They were probably married with children and had nothing in common with the students they were teaching. Today's 24 year-olds are barely removed from the high school mindset. They watch the same movies, listen to the same music, have the same interests and post the same crap on their myspace pages. They have so much in common with each other, it's not unusual that they'd forget their age differences and hook up.
In the past twenty years our Popular Culture has fostered Hypersexuality in Our Society.
We had female sexual predators when I was in high school, but they were a lot older and very unattractive. The one that I am thinking of was a Latin teacher who preferred the male athletes who were the same age as her own son.