I think its because we have the Internet so we are aware of it more.
Forty years ago in my high school it was happening. I can think of 3 very young attractive teachers who were sleeping with at least one student per teacher. Two were married, those marriages ended pronto, the one single one ended up pregnant. All left the school but stayed somewhere in the county system. In these 3 cases they were not much older then the students and in all 3 cases the male student was on the 6 year high school plan. So its not surprising looking back.
Pregnant!
There have been several posts from male Freepers implying that they wished their female teachers had been as beautiful and promiscuous. So??....How many 16 or 17 year old teen boys are ready for that responsibility? Would these posters who claimed to have yearned for this wanted that?
Also...Women who would do this are likely sociopaths and highly emotionally manipulative.
I seriously dated a man ( he wanted to marry me.) who had been seduced by a high school counselor. It was his first sexual experience. It was a painful and embarrassing memory for him and one that he would have preferred to not to have had.