The university dropout claimed various degrees he never obtained and used his father's legitimate teacher registration over a 24-year career between 1976 and 2000.

This spanned Victoria's Mount Scopus Memorial College, Haileybury College and Overnewton Anglican Community College. He also spent six years as a headmaster at Caulfield Grammar School over the 1980s and 1990s.

Now 72, Lennie has admitted in Victoria's County Court to four counts of obtaining a financial advantage by deception in the form of pay worth $843,567.

Former colleagues and students sang his praises in letters detailed to the court on Wednesday.

Leading infectious diseases expert and inaugural Doherty Institute director, Professor Sharon Lewin AO, said Lennie had taught her physics and described him as one of the most outstanding teachers she'd ever had.

"I often credit Mr Lennie with my enduring love of science, pursuit of academic excellence and self-belief in my own capabilities in science," she wrote in a letter to the court.

"I remember him very clearly telling me that I was capable of doing anything in life and to shoot for the stars.

"As a young woman in the 1970s, I now understand that this kind of encouragement for women in science was most unusual."

Discrepancies were discovered with Lennie's records held by the Victorian Institute of Teaching when he went to renew his registration. It was cancelled in 2009.

The institute in 2014 charged him over another role as headmaster at different school, again without qualification.

He was fined $8000 and in 2015 the institute referred him to police before criminal charges were laid in May 2020.

Notwithstanding his lies, Ian Hill QC said Lennie was an outstanding teacher who earned the respect of students and staff.

Prosecutor John Dickie said the case was not about whether Lennie had been a good or bad teacher, but about him lying about his qualifications and fraudulently obtaining money meant for legitimate teachers.

Lennie had enrolled in various science, maths, arts and business degrees and diplomas, but did not complete them or obtain any relevant qualification.

Mr Hill said Lennie began his teaching career legitimately in the 1960s when formal qualifications were not required to teach.

Lennie felt he'd found his calling and was driven by a misguided sense of vocation and Christian ideals instead of greed, the barrister added.

Lennie was sorry for lying, felt he'd been publicly disgraced and hoped "anyone I've harmed feels justice has been done", the court was told.

Judge Patricia Riddell indicated she was not inclined to jail Lennie and ordered he be assessed for a community correction order.

He remains on bail and is due to be sentenced later in March.

Australian Associated Press