Crown prosecutor Gavin Silbert QC has appealed the sentence imposed on Edward "Ted" Bales, who must serve a minimum of three years after he pleaded guilty to 34 historical child sex abuse charges.
Mr Silbert told the Victorian Court of Appeal that an 18-month portion of Bales's overall sentence was inadequate punishment for an "egregious" indecent assault on one of the boys.
The assault of the 11-year-old boy in his own home was close to the worst conceivable example of the offence and would constitute rape under current legislation, Mr Silbert said.
"There was a clear breach of trust. There has been no remorse apparent," Mr Silbert said.
Bales, formerly known as Edward Vernon Dowlan, changed his name to avoid the publicity of being associated with the convicted pedophiles alongside whom he taught at the St Alipius school in Ballarat.
The 65-year-old was jailed for historical child sex offences in the 1990s and the further six-year term was imposed in March after Bales pleaded guilty to another 34 charges for abuse in the 1970s and 1980s.
In his appeal, Mr Silbert also criticised the "totally out-of-kilter" way in which Bales's concurrent prison terms were being served.
"There seems to be no logicality in the way the amounts of cumulation are calculated," he said.
Defence barrister David Hallowes said the 18 months' jail imposed for the indecent assault was well within range and Bales had pleaded guilty at an early opportunity.
He said Bales hadn't offended since 1985, indicating his rehabilitation was complete.
The court has reserved its decision.