Keith Ellerton, 75, of Allansford, pleaded guilty in Warrnambool County Court last Friday to historic child sex offences.

The indecent assault charges included one rolled-up charge involving a series of separate offences dating back to 1992. The offending did not happen at a school.

The court heard the first charge related to offending between 1992 and 1995.

The offending involved Ellerton touching a girl aged under 16 on her breasts on eight separate occasions.

On Wednesday Ellerton was jailed for four years with a non-parole period of two years.

Judge Frances Hogan said the man was entitled to a significant discount to his early and "remorseful pleas" of guilty which meant the victim was not required to give evidence in a trial.

She said Ellerton was someone who should have protected the girl and not abused her.

"You as a primary school teacher and headmaster should have been acutely aware of the pschosexual stages of development of children and how very vulnerable a child is as she approaches and goes through her phase of puberty," the judge said.

"You should have known how harmful exposure to inappropriate sexual conduct can be before a child has the maturity to understand, yet twice in your record of interview, you refer to yourself as being 'naive'.

"You told police that although your victim had a couple of times said 'don't' you were 'naive enough to continue on'."

Judge Hogan said Ellerton not only "intruded on the innocence of (the victim's) childhood but created confusion,eroded her self esteem and made her feel powerless".

"Your moral culpability for this offending is high because you knew it was wrong but selfishly put your own desire and some sort of sexual satisfaction before your victim's welfare," she said.

She said the offending had a "degree of planning" because Ellerton ensured it occurred when he and the victim were alone.

"It was persistent and predatory in nature in that you repeatedly ensured you had the victim on your own," the judge said.

Lawyer Markorius Habib said in the plea hearing that Ellerton had shown "genuine remorse" through not only his admissions to police, but a letter of apology given to the victim some years ago.

He said Ellerton was a former dairy farmer, teacher and principal at a number of schools throughout western Victoria, and a volunteer at the Allansford Cricket Club and local cricket association.

Judge Hogan accepted that Ellerton was "extensively a model citizen in the community" and had made generous contributions to sporting organisation.

But, she said he "behaved in a depraved way".

The judge said if not for Ellerton's guilty plea, he would have been jailed for five-and-a-half years.

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