Here is an idea for a story of the blackmailed teacher's type.
the teacher has a daughter in the high school where she teaches.
her daughter fights in the breaks with a group of girls that are in the same class where she teaches. the fight get worse, neither of them (the girls) wants to give up. so it really get aggressive but nothing sexual. finally the teacher get involve ,and trying to protect her daughter ,reprehends the girls from her class, she gives bad notes to the girls and they go to the principal and they insult one another finally the girls decide to take reprisal with the teacher, so they appeal to the new boyfriend of the teacher's daughter and convice him to take pictures of her girlfriend naked and seduce the friends of the girl ,with that they go to the teacher and show her how vulnerable is her dauther and how they can humiliate her and make her do terrible things, unless the teacher agreas to take her daughter's place. so finally her humiliation begins and they turn her into a slave, and in the breaks they make her fuck with some students in the toilet and same times takes her blindfolded to other places and make her fuck with students that she can't recognise. and make special meeting and so on..
i hope you like it and know english better than me. and write a nice story. bye