James William Treasure, 42, filmed himself having intercourse with sex dolls, wearing masks made from school photos of his current and former students.

Treasure had already been jailed in Queensland after police caught him filming children on a Noosa beach in 2018.

When Queensland detectives searched his accommodation, they found 3900 child abuse images stored on his laptop, as well as shoes fitted with secret recording devices.

They also uncovered videos of him having intercourse with a childlike sex doll in a school uniform, and films of sex acts on which he had digitally imposed his own face and that of one of his students.

While Treasure was still in Queensland, Victorian police raided his Melbourne home, uncovering dozens of CDs, DVDs and hard drives of child abuse material, almost 100 videos he had filmed of children, and three covert watch cameras.

Treasure had also collected 30,000 videos and images of activities from the schools where he taught, the court heard, and he kept a diary of his interactions with students.

Treasure was granted parole in Queensland in January 2021 and now faces a jail term for his child sex crimes in Victoria.

In the Victorian County Court on Monday, he pleaded guilty to charges of producing and possessing child abuse material, and two counts of an indecent act with a child under 16.

The court heard Treasure would prey on his students by inviting them into his classroom at lunchtime, giving one of his victims chocolates before kneeling down and tickling her, and then touching her vagina outside her shorts.

After she yelled out a swearword, Treasure reprimanded her, saying she had gone too far, and other children would have overheard.

Another former student described him tickling one of them in "weird or wrong places" on five or six occasions.

A victim impact statement read to the court described one of his victims as a "bright happy and confident" student, who in the years after Treasure preyed on her, began to have mental health problems and use drugs and alcohol.

Judge Frances Hogan described Treasure's offending as disturbing and an enormous breach of trust, with some victims still unaware he had filmed them over the years.

"The most grave aspect is the utilisation of his position as a primary school teacher, who parents are entitled to expect will protect their children," she said.

Defence lawyer Philip Dunn QC said his client obviously has a paedophilic disorder, but is taking the first steps on a long path to rehabilitation.

He said Treasure was mortified by his conduct and was open to using a chemical sex drive inhibitor to stop his offending.

But prosecutor Francesca Holmes argued Treasure's insight into some of his offending was nonexistent, especially when it came to abusing his students.

She said he does not acknowledge sexual deviance was driving his offending.

"He has a history of sating his sex drive by exploiting children, and he is only just coming to terms with that," she said.

The court has ordered a pre-sentence forensic psychiatric assessment.

Treasure will be placed on a sex offenders register for life and will return to court for further plea on January 31.

Australian Associated Press