Neil Lennie, disgraced former Melbourne school principal, has been ordered to pay back the half a million in wages he earned after he was exposed as a fraud.

He claimed he had various degrees and used his father's legitimate teaching registration over a 24-year career between 1976 and 2000.

He worked across Victoria's Mount Scopus Memorial College, Haileybury College and Overnewton Anglican Community College.

Lennie admitted in Victoria's County Court to four counts of obtaining a financial advantage by deception to the tune of $843,567.

He was also sentenced to three months in jail which was wholly suspended as well as being given a 12-month community corrections order.

He has since been ordered to pay back $500,000 in earnings as the judge found that his lies caused no loss or harm.

References also described him as an "excellent educator", with leading infectious diseases expert Professor Sharon Lewin AO describing him as the best teacher 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.”

Photo credits: 7NEWS