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.
In one of the cases she married the student. He was on the 6 year high school plan. They were within 3 years or so in age. I have no idea if the marriage lasted, but I doubt it.