Lamb by Bernard MacLaverty (Penguin Books 1980)

'Ah, Brother Sebastian. I was expecting you.'

Michael began, the words becoming slurred in his haste to get them out before his courage failed him.
'Brother Benedict, I must protest in the strongest possible terms about the . . . the thrashing you have just given Owen Kane.'

'And why is that?'

'He did not sign his name to any slogan.'

'Brother Sebastian, I'll thank you to calm yourself.'

'Did you say that the boy signed his initials to some graffiti?'

'I did.'

'O.K. is a slogan itself. They just add it to things.'

Brother Benedict took off his glasses, folded the legs flat and rubbed into the corners of his eyes with finger and thumb.

Brother Sebastian, do you think I'm a fool? Credit me with a little lore intelligence.'

Michael did not know how to react. He was confused.

'You know and I know,' said Brother Benedict, 'that we could never find the real culprit. By now the boys know that punishment has been meted out. Someone has got it in the neck. It may deter others from doing the like again, for fear their mates get it. The O.K. is just a little irony of mine. "Benny dies O.K." Now the boys know that Benny has risen.' He bunched his big fist and swung it in a slow punch, clicking his tongue at the supposed moment of impact.

'K.O.,' he said with satisfaction.

For the next week Owen had to try and clean the slogan off with a pad of steel wool. To reach it he had to stand on a stool.