It is understood the allegations against the former headmaster of St Gregory's Primary School, Marist Brother Charles Giuliani, have not previously been reported publicly.

Documents filed in the ACT Supreme Court on behalf of the plaintiff alleged Brother Giuliani "sexually assaulted the plaintiff on numerous occasions" while the plaintiff was a student in his care between 1962 and 1966.

Originally filed in November 2015, the case was settled last month, without any admission of guilt, between the plaintiff, the Estate of Charles Giuliani and the Trustees of the Marist Brothers.

A spokesman for the Marist Brothers Province of Australia said that where a settlement was reached, it was "not a finding of criminal conduct, however it is recognition that some trauma has been sustained by the claimant involved".

"Whilst prior to his death Brother Giuliani consistently denied any wrongdoing, it was recognised that the claimant in this matter had sustained trauma most likely during his time at school," he said.

"As a result a settlement in this instance was made in line with our approach."

The school was operated by the Marist Brothers between 1962 and 1984, before a number of Catholic schools in the New South Wales town were amalgamated in 1987.

It was unrelated to a school bearing the same name in Queanbeyan, now operating under the auspices of St Gregory's Parish and the Archdiocese of Canberra and Goulburn Catholic Education Office.

Lawyers for Brother Giuliani rejected the abuse allegations, but did not dispute he was headmaster of the school at the time.

But the defence files showed Marist Brothers could not confirm whether the alleged victim of the sexual assault was a student at the time, as the school records were unavailable "as they were destroyed in a fire".

Documents filed by the defence also rejected the entitlement of the plaintiff to any costs or damages related to the alleged assaults, under the statute of limitations, "as the claim was brought after the expiry of the limitation period".

The case was originally brought against Brother Giuliani, the Marist Brothers organisation and nine other defendants who held various senior positions within the Catholic order, as the plaintiff was in doubt as to who to bring legal proceedings against.

But the scope of the plaintiff's case was later limited to those with direct responsibility for St Gregory's Primary School at the time.

They included Brother Giuliani and the then-Provincial Leader of the of the Marist Brothers Sydney Province, a position held by Brother Quentin Duffy between 1962 and 1964 and Brother Othmar Weldon from 1964 to 1966.

The Royal Commission into Institutional Responses to Child Sexual Abuse has previously found that both Brother Duffy and Weldon "took no, or no adequate, steps" to ensure the convicted child sex offender, Brother John "Kostka" Chute, did not have contact with children through his work.

However, there is no evidence as to what steps Brothers Duffy and Weldon did or did not take in relation to the allegations of abuse against Brother Giuliani.

The defence admitted that Brothers Duffy and Weldon "owed the plaintiff a non-delegable duty of care to ensure that reasonable care was taken for the plaintiff's safety", but did not admit that that duty was breached.

Documents also show the defence denied claims Brothers Duffy and Weldon were "vicariously liable" for the alleged abuse and associated "injury and harm suffered by the plaintiff".

The Marist Brothers spokesman said the order was "committed to resolving civil matters with a victim-focused approach" and that the order refrains from discussing the details of negotiations and settlements.

"We reiterate our encouragement to any person with any complaint to make contact with our Office of Professional Standards on (02) 9218 4000," he said.

"We urge any person with any evidence of criminal conduct to take that to the police."