A former Christian Brother beat orphans who tried to get away from his violent sexual attacks and warned them not to tell anyone, the Victorian County Court has been told.

Fifty years after William Stuart Houston preyed on six vulnerable boys at the St Augustine's Orphanage, which was run by the Christian Brothers in Geelong, the 77-year-old has been jailed for 12 years and nine months.

A jury found him guilty of abusing three victims and he then pleaded guilty to indecently assaulting three other boys.

He must serve at least eight years and may end up dying in jail.

"Justice was done," declared the wife of one victim.

Her husband said there was no-one the boys could turn to.

"We were just children. Totally defenceless, that's what we were, and him saying 'This is our little secret, don't tell anybody'," he said outside the court.

'Virtually impossible' for a child to complain

Chief Judge Peter Kidd said the frightened boys were powerless to stop Houston, who showed a contemptuous indifference to their cries of pain and protest.

"Tragically the complaints or partial complaints of three of your victims were variously met with denials and physical punishment by other staff members at the orphanage," Judge Kidd said.

"The reaction of staff simply serves to demonstrate how it was virtually impossible for a child in those circumstances to come forward and meaningfully pursue a complaint.

"It also explains how you were able to continue to offend in this disturbing atmosphere of impunity."

He said the boys abused by Houston were especially vulnerable: young wards of the state who were under his control.

Houston was meant to protect and nurture them.

"Instead you arrogantly abused your authority over each of them for your own perverse sexual gratification," Judge Kidd said.

"What occurred here amounted to a disgraceful breach of trust."

'Deplorable' betrayal of trust

The Christian Brothers Oceania described Houston's offending as shocking and offered an unreserved apology.

"That any young person placed in our care has been abused as these children were by this man is a matter of great regret and remorse for all Christian Brothers," the order said in a statement.

"The Christian Brothers Oceania views these actions as a deplorable betrayal of the trust of innocent children and their families."

Houston left the order in 2008.

Judge Kidd said Houston had led an apparently blameless life since abusing the boys, aged between 10 and 14, over seven years at St Augustine's in the 1960s.

Houston had not offended since, despite teaching boys at a number of Melbourne and regional Victorian schools.

But the judge said Houston had shown no remorse.

"You have never really confronted what you did to these boys, let alone atoned for your wrongdoing," Judge Kidd said.

Houston was a dormitory supervisor to four of the victims.

Leonie Sheedy, from CLAN, a sex abuse victim support group, said she was extremely happy for the victims who came forward recently and told police about the abuse.

"There is certainly an element of a victory here for victims that they've now been believed," she said.

"I hope that they can you know maybe just get some comfort knowing that he will die in prison."

AAP/ABC