An 84-year-old Christian Brother has been jailed for sexually abusing a young boy when he was a teacher at a Catholic college in Kalgoorlie more than 50 years ago.

James Brian Hamilton pleaded guilty to indecently dealing with the student when he was about 12 or 13 years old, in 1964.

Hamilton was aged 29 or 30 at the time when he forced the boy into an army cadet store shed before tying his hands behind and back and assaulting him for up to 15 minutes.

The District Court was told the boy yelled for help but no one came to his assistance, and after the abuse was over he told Hamilton "This will never happen again".

The victim, who is now in his 60s, read his victim impact statement to the court, describing how the abuse had caused him "lifelong distress" and years of "sadness, pain and upset".

"I was tied up. My liberty was forcibly curtailed and I was detained for Hamilton's depraved indecencies to occur," he said.

"What an injustice, tying up a 13-year-old and then subjecting his victim to sexual abuse of the grossest kind."

The man detailed how, over the following years, the Catholic Church refused to acknowledge or believe his complaints, at one point even threatening him with legal action.

"They made me feel insignificant and caused me great stress and pain … [they] have denied me honesty, justice or consideration."

The man said he complained to police in the 1990s, but again nothing was done, and it was not until after the recent royal commission into child sexual abuse that Hamilton was charged.

Hamilton's lawyer, Fiona Todd, urged Judge Laurie Levy to consider imposing a suspended jail term, arguing her client was a very old man with significant health problems, whose time in jail would be difficult because all of his family and supporters were in Melbourne where he had been living in a home for retired Christian Brothers.

However Judge Levy said the offence was too serious and an immediate jail term was the appropriate penalty.

Judge Levy said aggravating features of the offence included that Hamilton was a teacher and the victim was a student, that the boy was very vulnerable and that Hamilton had used a level of violence against him.

"He clearly suffered both physical and psychological abuse at your hands."

Judge Levy took into account Hamilton's age, his ill health and his plea of guilty, in deciding to impose the two-and-a-half year term.

Hamilton will have to serve 15 months before he can be released.

Apology too little, too late

Outside the court, the victim said he was pleased with the sentence and believed that, decades later, justice had finally been done.

"It was a long time ago that these events occurred but I personally believe that age should not be a factor," he said.

If you do something wrong, and something terribly wrong then you have to be accountable for that."

"I think it also sends a very clear message to the Christian Brothers who really, as an organisation, have to get their act together."

The man said he had, in the past few days, received a letter of apology from Hamilton but it was "basically too little, too late".

He said he hoped that now Hamilton had been sentenced, some of the pain and suffering he was still suffering would be eased.

"I've got to enjoy the rest of my life and have some sort of peace, so I'm going to try really hard to make the most of enjoying my life."

"I will always be a strong advocate for protecting children from all harm, from physical harm as well as sexual harm."

The Christian Brothers Oceania Province released a statement after the sentencing.

"We deeply regret that any child has suffered abuse and we apologise unreservedly," the statement read.

"We acknowledge the sentence of the court and hope that the process of justice provides some sense of healing."