A Catholic priest who viewed a NSW school where he taught as a “pedophilic smorgasbord” has been sentenced to a further 13 years for his abuse of 18 boys.

John Sidney Denham, 73, is already in the middle of a jail term, handed to him in 2010 for his sexual assault of boys as young as five.

But on Friday, Judge Helen Syme sentenced the priest to another 13 years jail for charges stemming from his abuse of 18 boys at St Pius X in the Hunter in the 1970s.

Adding the new charges, Judge Syme calculated Denham had abused 57 children, some repeatedly.

“At St Pius X, the offender operated as if he was at some pedophilic smorgasbord, entitled to abuse boys at any time or place of his choosing,” she told the Downing Centre District Court in Sydney.

“It defies belief that his abuse of children was not only widely known but ignored or condoned by those in authority.”

The boys were attacked in public and private – in the playground, in the principal’s office and even outside the confessional.

He will be eligible for parole in 2028.