He worked out that he received about $750 in compensation for each time he was molested at Geelong Grammar.

From the age of 11, he was abused by former boarding house assistant Philippe Trutmann – between 30 and 40 times.

The softly-spoken IT consultant believes the $26,000 settlement he received from the school in 2007 is "manifestly unjust" in light of what he now knows.

The 41-year-old is trying to negotiate a top-up payment, but feels he's getting nowhere with his former school.

"It feels like I'm being put through a machine again, by one of the country's wealthiest schools," he said.

"There's a difference between what they say and what they do."

It was revealed during the Royal Commission into Institutional Responses to Child Sex Abuse that Geelong Grammar repeatedly failed to act on allegations of improper conduct involving Trutmann.

The school first received these allegations in 1985.

Institutional abuse lawyer Angela Sdrinis said Mr Benson would not have been abused in 1988 and 1989 if the school had acted on these claims.

"They talk about restorative engagement but we haven't experienced that," Ms Sdrinis said. "What we've experienced is brick walls and legalistic arguments."

In a bid to negotiate a better deal, Ms Sdrinis is considering taking legal action on behalf of Mr Benson, another former Geelong Grammar student and Catholic church sexual abuse victims to set aside their settlement deeds.

But it's a risky proposition. If they lose, they could have to pay the institutions' legal costs.

Ms Sdrinis said it shouldn't be so difficult.

She has worked with other schools, including some run by the Christian Brothers, who have topped up settlements without the same adversarial legal approach.

Geelong Grammar principal Stephen Meek said he was unable to discuss individual cases.

He said the legal system was adversarial but the school had tried to make the process as smooth as possible.

"There can be a debate about what is an appropriate figure of compensation, but the school has accepted its responsibilities when its former staff have abused the trust which was placed in them," Mr Meek said.

"There could be an attraction to having a less adversarial approach to a settlement, but it would need to be legally binding on the parties."

He said the school also offered victims an apology, counselling, contact with the school's survivor liaison coordinator and a restorative engagement process which "gives a greater sense of closure".

"The school is always very sorry that there have been victims of child sexual abuse and wants to help the survivors," Mr Meek said.

The Royal Commission will deliver its final report to the Governor General on Friday.

It's hoped that the Turnbull government's national redress scheme will make it easier for some sexual abuse victims to receive top-ups to previously inadequate compensation.

However, there is no guarantee that victims like Mr Benson will be able to access the scheme because states and institutions must first opt in.

His life changed forever when he was asked to attend Prahran police station one autumn day in 2005.

Police told Mr Benson that Trutmann had admitted to sexually abusing him up to 40 times over two years. He had no clear recollection of these crimes.

Trutmann, who was convicted in 2005 of sexually abusing 40 students and sentenced to 6½ years' jail, had identified Mr Benson from school yearbooks, circling his face in pen.

"I remember leaving the police station and I just cried," Mr Benson told the Royal Commission's public hearing into Geelong Grammar in 2015.

Some of the painful memories have since flooded back.

He remembers Trutmann creeping into his room in the middle of night, and coming over to his bed with a flashlight.

He remembers more painful details now about Trutmann's constant grooming and the massages in his bed after lights-out.

Much of the abuse took place later in the night, while boys slept, or pretended to sleep, crippled with fear. Many of Trutmann's other victims also couldn't recall the specifics of his crimes.

Mr Benson has been diagnosed with post-traumatic stress disorder, anxiety disorder and depression. He said it was fortunate that he has got supportive friends, family and colleagues.

"They have been the ones who have helped me through some pretty difficult and dark times."

Beyond Blue: 1300 22 4636

Sexual Assault Crisis Line (Victoria) 1800 806 292