I don't know what grounds our rumour had, but the guy disappeared and never came back, and naturally there were all sorts of crazy ideas people had. Some claimed he punched a student, some claimed he was a pedo, some claimed he showed porn in a lesson in front of the head, some claimed he was storing porn on the school computers but really when I sat and thought about it, the most logical reason I could think of was that the random 2 weeks holiday he took in the middle of a term was unsolicited and against the rules. Who knows though.