NSW teacher 11 year sentence for abuse

A former deputy principal has been sentenced to 11 years in prison for sexually abusing two young sisters at his NSW home.

The girls, who cannot be named for legal reasons, were seven and nine when their parents dropped them off at the home of Mark Robert Forbes and his then wife in Wollongong on March 27 last year.

At the time the now 54-year-old was a deputy principal.

During the evening, the court heard that Forbes' wife had dinner with the two girls as he stayed in his study drinking.

When he finally emerged he sat down with the two girls and indecently assaulted them while his wife was in another room.

Later that evening when the youngest girl was alone in a bedroom, Forbes sexually assaulted her, telling her to "keep it a secret".

In sentencing him on Tuesday to five counts of indecent assault and one count of aggravated sexual intercourse, Judge Mark Marien said Forbes had committed a gross breach of trust.

"The offender's prior good character and good reputation as a teacher ... enabled him to be entrusted with the victims," he told Sydney's District Court.

He said he was unable to judge his prospects of rehabilitation as Forbes had shown no remorse and continued to deny any guilt.

The court has previously heard that the girls began crying after the abuse and confided in Forbes' wife.

She immediately contacted the girls' parents and took them home.

The police were later contacted.

The court heard Forbes had ruined his career and marriage as a result of the abuse.

The girls' mother previously told the court that his actions had created a chain of events like when a "stone is thrown into a pond".

"Since the incident we have shied away from socialising. Our whole family has been traumatised ... (It) has shaken our sense of trust with people ... I'm not sure if we will ever be the same again."

Judge Marien sentenced Forbes to a maximum of 11 years in prison and a minimum of five-and-a-half.

Taking into account time already served, he will be eligible for parole in October 2019.