Ballarat Magistrates Court heard Stephen Francis Farrell, 62, of Balwyn North, was 22 years old when he assaulted the boy.

The latest victim became Farrell's third after he was convicted in 1997 of nine counts of indecent assault stemming from acts he committed on two nine-year-old boys, also pupils at St Alipius during the same period.

Farrell avoided jail in 1997. Yesterday, the court heard Farrell was teaching the victim during an art class in late 1974 when the victim spilt paint on his pants.

Crown prosecutor Raelene Maxwell, who called for the immediate imprisonment of Farrell, said Farrell told the victim to go straight to the sick bay and take his pants off.

A short time later Farrell also went to the sick bay and indecently assaulted the boy.

Ms Maxwell said the boy "completely froze" before running home and telling his mother of the assault. The court heard the victim's mother later discussed the assault with former St Patrick's College headmaster Paul Nangle.

Sarah Leighfield, for Farrell, said while her client accepted he was guilty of the offence, he had no memory of the actual incident.

Describing the offence as "a serious, mid-level, indecent assault", Ms Leighfield said Farrell, who is now in his third marriage with two children, was extremely remorseful and hadn't re-offended since 1974.

The court heard Farrell "hated who he was" at the time of the offence and left the Christian brotherhood a short time after. The offence wasn't brought to police attention until 2012.

Ms Leighfield said Farrell had joined the Christian brotherhood as a 16-year-old and had never had the chance to develop his sexuality.

Ms Leighfield asked magistrate Michelle Hodgson to suspend any potential jail term, adding Farrell had had bouts of depression and suicidal thoughts which would be heightened in prison.

Seated next to his wife and two other supporters yesterday, Farrell showed little emotion as Ms Hodgson said she would reserve her sentence until December 19.

 Outside court Farrell ran from the media with a folder shielding his face.