A judge has choked back tears as he condemned a pedophile priest for plunging to "the depths of evil hypocrisy" by abusing vulnerable schoolboys.

Victorian County Court Judge Frank Gucciardo said Frank Klep used vulnerable young men for his "vile sexual gratification".

Klep preyed on boarders and sick children sent to his care at the infirmary he controlled at Salesian College, Rupertswood, and continued the abuse when he returned to the school as principal.

He abused more than two dozen boys at the school in the 1970s and 1980s, knowing his position of authority would keep his victims silent.

Judge Gucciardo became emotional and had to leave the courtroom on Monday as he described the suffering of 15 of Klep's victims.

"The young men you have abused were broken by your conduct," Judge Gucciardo told Klep.

"There is no doubt your conduct plummets the depths of evil hypocrisy."

Judge Gucciardo jailed Klep for 10 years and six months, with a non-parole period of six and a half years.

Klep admitted abusing 15 boys, often after they had been sent to the school infirmary. He also pinned a boy down on a bed and raped him.

When a boy he was abusing asked him what he was doing, Klep replied that it was natural.

Judge Gucciardo said Klep knew his position of authority as a priest and teacher would prevent his victims from coming forward.

The boys who tried to tell their parents were not believed, Judge Gucciardo said.

He said Klep used vulnerable young men for his "vile sexual gratification".

Klep, 70, pleaded guilty to 15 counts of indecent assault, buggery, attempted buggery and rape and has now been convicted of abusing a total of 28 children.

Broken Rites researcher Dr Bernard Barrett said Klep was inflicted upon his victims as the Catholic Church looked the other way.

"It's not just what he did with his left hand or his right hand, it's what he was allowed to do," he told reporters outside court.

"Their parents trusted the church in those days. Those days are gone."

After being convicted in 1994 of indecently touching two boys, the Salesians sent Klep to Samoa, where he continued to work as a priest.

A Victorian parliamentary inquiry found that Klep and another member of the order lied to Samoan authorities about his criminal record.

After the Samoan government began a deportation hearing, Klep returned to Australia voluntarily in 2004.

He was sentenced to at least three and a half years in jail after pleading guilty in 2005 to indecently assaulting 11 boys.

Klep was defrocked in 2006.

A plea hearing last month was told Klep had suffered a spectacular fall from grace and that he was a pariah known as the "pedophile priest" wherever he went.

Klep read an apology during the plea hearing, but many of his victims left the courtroom as he spoke.

Judge Gucciardo said he accepted that Klep was remorseful and had a low risk of reoffending.