The teacher was not identified, nor is it completely clear how much of the second film in Tom Six's trilogy was screened before the complaint. A press release sent to the Sun states, "At the time the incident was reported, the teacher was immediately suspended and remains suspended pending the outcome of the investigation."
As The Wrap states, it is unclear if the teacher intended to show the film to students or if one of the students pushed play as a prank. Either is a possibility. When I was in high school, one of my English teachers had a sub show us the nuclear war scare film Testament for reasons he never adequately explained.
Six, ever the trickster, had his own take on the matter:
It should be mandatory to watch THC2 in school classes. It deals with a character that is bullied and what to do!https://t.co/hT3tGJu1qZ
— Tom Six (@tom_six) April 28, 2016
Personally, I find The Human Centipede (First Sequence) the most watchable of the series and a better choice for school-hours viewing.