A former teacher from one of Australia's most distinguished families of judges is likely to avoid jail, despite being convicted of possessing child abuse material.

Robert Emmett, son of NSW Court of Appeal judge Arthur Emmett and Federal Circuit Court judge Sylvia Emmett, was arrested in 2013 for possessing up to 10,000 child abuse images, some involving bestiality, pain and humiliation.

Emmett's grandfather is Sir Laurence Street, former Chief Justice of the NSW Supreme Court, a position also held by his father Sir Kenneth Street and his father Sir Philip Street.

Robert Emmett, a former maths teacher at St Andrew's Cathedral School, pleaded guilty to charges that included filming the private parts of children and possessing child abuse material.

In the NSW District Court, a sentencing judge said Emmett was remorseful and had no prior convictions.

The court heard the offender had been diagnosed with psychosexual problems and is receiving treatment.

The court heard Emmett walked around St Andrew's filming some students on his camera phone and, on one occasion, pretended to tie his shoelace while crouching down to film up a girl's dress at Town Hall Station in the CBD.

Some images in the 'worst category of abuse'

District Court judge Ian McClintock said some of the images found in Emmett's possession were in the "worst category of abuse", involving pain, bestiality and humiliation.

The court heard the images were photos and videos, but it was not clear how he acquired all of them.

"There is no evidence the child abuse material was for anything but personal use," the judge said, adding that some of the images were disturbing.

He said Emmett secretly videoed three schoolgirls aged 14.

"In my view it is a significant aggravating feature that the offender was a school teacher," the judge said, noting that Emmett abused his position of trust.

He referred to the "significant violation" of the students' rights.

Judge McClintock said Emmett's family was not aware of his activities and that the 38-year-old had a good support network to help with his rehabilitation.

The court heard Emmett was remorseful, timid and shy and would need to be in a high level of protective custody in jail.

It heard the publicity surrounding the case had been humiliating for the offender and his family.

"He's lost his career," the judge said.

"Nothing other than a sentence of imprisonment is warranted."

But Judge McClintock emphasised a sentence of less than two years was appropriate and therefore the offender is suitable to be assessed for an Intensive Correction Order — meaning he may be able to serve his sentence in the community.

Emmett remained on bail and will return to court in July.

He faced a maximum sentence of 10 years for possessing child abuse material and a maximum of five for filming a person's private parts.