Royal commission documents have exposed Marist College in Canberra as the most notorious Catholic school in Australia for child sexual abuse claims.
The Royal Commission into Institutional Responses to Child Sexual Abuse has revealed 63 claims of child sexual abuse made against the school.
But Bravehearts ambassador Damian De Marco believed the total number of victims at Marist College Canberra would be much higher.
"The true figure at Marist would be well over 100 given the number of stories I have heard about people who will never present officially and those that have died from suicide and drugs," Mr De Marco said.
While claims of child sexual abuse were made about 1049 separate Catholic Church institutions, the report singled out 28 institutions that had more than 20 claims of child abuse against them.
It showed orphanages and residential care facilities were the places most rife with child abuse - BoysTown in Beaudesert had 219 claims of abuse recorded against it.
The day the report was released, Marist College principal Richard Sidorko wrote to parents saying he still did not understand how boys could be abused at the school.
He said the legacy of the abuse "cast a shadow" on the school.
"I do not understand how a school with Marist's values and ethos could not protect the victims. But those evils occurred and innocent lives were damaged. I know I speak on behalf of all Marists when I say we are horrified by these tragic events. They should not have happened," Mr Sidorko wrote.
He said the "seemingly constant flow of media reports" was damaging for morale.
"The abuse we get on social media, the name calling and the graffiti on our signs, these acts could sow the seeds of doubt about why we bother to stay here," Mr Sidorko said.
"The number of cases of abuse and the number of abusers across the religious orders, the priesthood and the laity reflects very badly on our church.
"It would be understandable if Marist people lost faith in the College and what it stands for."
He asked the school community to keep a "fair view" about the proportion of abusers identified in the Marist order during royal commission proceedings.
"From 1968 until 2015 over 100 Marist Brothers have served in a variety of roles in our college. A small fraction of them abused boys," he wrote.
"The large percentage of brothers tried faithfully to live out their vocation, committing their energies to the boys in their care.
"While 20 per cent of Marist Brothers in Australia are known to have been abusers, we must also remember 80 per cent, four out of five, did not."
A relationship banned under traditional law.
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