Drago Kamenik, 41, was apparently found by students between the legs of 45-year-old brunette Manja Mertelj after they heard moans of pleasure coming from a classroom they believed to be empty.
And the embarrassed headteacher first threatened to sue students who uploaded a clip of the pair onto social media and then denied it was real after the clip went viral.
‘We heard the noises and knew someone was having sex in there,’ said one 19-year-old student at the high school in Maribor, Slovenia.
‘But we thought it would be other students. We couldn’t believe it when we saw our maths teacher and headmaster.’
Married father-of-two Mr Kamenik still claims the video is fake, and says he has reported the clip to police, according to Slovenske Novice.
‘The man in the video is not me, it has been photoshopped,’ he said.
‘I also spoke to my wife. Can these fools even begin to imagine what damage they have caused by doing this?!
‘As for the maths teacher, she is a very good teacher and has had many positive things said about her.’
Students dismissed his threats, however, adding that they are willing to put up the rest of the footage – which they say shows clearly who is involved – if necessary.
‘We can put up more to prove it but I don’t think anyone really doubts us,’ said one student on social media.