This will sound like fiction, but it's really not.
There was this biology teacher that was very charismatic, he claimed to be an anatomy professor at a local university, but he liked teaching at our school out of vocation, and trying to prepare people to study medicine.
He suffered from diabetes, which meant that some times he would just leave a classroom and go somewhere (he said he went to the teacher's lounge to rest for a bit).
Now, here the odd stuff starts to show, he also had "a twin brother", now, this sounds pretty silly in retrospective, but people believed him, and some days, his twin would come to the school to "excuse his brother" because he was sick or something.
All of this was pretty odd, but people accepted it and eventually regarded it as some curious fact and nothing more, until the Pink Day happened.
Now, the Pink Day was some school festivity that some group started and the school allowed it, and it was about girls sending gifts to guys during class hours, similar to St Valentine, but there was something else...the girls were allowed to grab guys out of the classroom and bring them "somewhere", this somewhere was the gym, and there they would dance and kiss them, it was a pretty sexual thing that in retrospective (again) could've been avoided by the school.
The thing is, with this teacher, is that one year, after Pink Day, some parents got sent to their homes, envelopes containing photos with explicit sexual content performed by minors in the school (minors being teens above the age of 14, but still minors) that took place during "Pink Day" on some place inside the school. This school was particular in that, it was composed of many buildings on the same street, but the pictures showed some sort of abandoned classroom (probably one on one of the buildings that was being remodeled). The parents got very upset and demanded an explanation from the school and threatened to go to the press (in the end they didn't, for some reason), the school cancelled Pink Day forever, and decided to investigate, they interrogated the students that appeared on the pictures but nobody would say a thing, and then, this teacher disappears.
Later that year the students started talking about what truly happened and everything was uncovered. This biology teacher had offered them to make them pass his class if they would get together, have sex while taking pictures of it as if it was part of the Pink Day stuff (some guys blindfolded strapped on chairs while girls sucked them or stripped and then ended with sex), and then send him the pictures, stating that he was going to have "revenge" from the school, and since this kids were doing really bad at school they kind of got behind the idea of harming the school this way.
Then more truths began to raise to the surface about this teacher.
He wasn't an anatomy teacher at university, he just attended one year to medicine in that university, he wasn't a teacher at all, he didn't have a twin (duh), he didn't suffer from diabetes, he had sent the pictures to the parents from different post offices so they wouldn't be able to track him, and on another region of my country, he was being looked for by the police for fraud.
But he wasn't just a conman, he was a great manipulator too, I had an experience with him when I attended some science contest at one university and he was in charge of taking us there and act as our warden, as soon as we stepped outside of the school building he started convincing us that we were doing some favor to the school and that the school should pay us to participate on a contest on under "the school banner", in the end we won and he somehow convinced everyone that the prize shouldn't go back to the school, but where should it go? dividing it and keeping it seemed unethical (duh again...) so he lead the discussion to the point that the fair thing to do was to...give it to him.
After some years, out of school and on my college years, I came to learn that some people have seen him on a nearby school (near to my previous school), with another name, acting as a chemistry teacher. And we learned too that the police had been looking for him all this time, and that he was dangerous, see, he did had some relation with medicine school: he had cut someone on the face (disfiguring him) with a scalpel, when he was confronted for a previous scam, in which he was acting as a pharmacist.
To this day, I'm still surprised that the press didn't get involved, but I believe that in the end the parents didn't want to drag the school down for what some sick guy would've done, because in the end, that's what he wanted, to destroy the school's name.
But why did he want to do that? Well, it seems that he was hitting on the director, but she rejected him.