A teacher blindfolded children as young as eight and fed them cookies laced with his own semen.

Mark Berndt faces a 25-year jail sentence after admitting more than 20 abuse charges against around 30 pupils over a five-year period.

The 62-year-old was removed from the classroom at Miramonte Elementary School, in Los Angeles, in the US, in 2011 but is suspected of abusing children as far back as the 1990s.

His crimes were uncovered when a photo technician passed on images of blindfolded and gagged children, some of whom had cockroaches on their faces, he had been asked to develop to police, who later found a spoon with Berndt’s semen on it in a classroom bin.

John Manly, a lawyer acting for the victims and their parents, said of the guilty pleas: ‘He’s going to jail essentially for the rest of his life. You can’t ask for more than that.

‘For all intents and purposes, this man murdered these children emotionally.’

The school authority is facing dozens of lawsuits from parents over the abuse, while another teacher, Martin Springer, is also awaiting trial after being charged with lewd acts against a child between seven and eight years old.