Little did she know that a teachers' aide, Sergio Edward Montoya???, was taking photographs of her underwear as she played at Forest Lodge Public School.

Montoya, 48, was working as a learning support officer at the Bridge Road School for special needs children, and was supposed to help young students settle into mainstream schools.

Instead, the former dancer, who gained some prominence in the 1990s when he won Channel Ten's Star Search, took 14 iPhone photographs focusing on the girl's crotch at the inner-west school in February 2015.

He also took 13 similar photos of another child at the Bridge Road School in late 2014.

"There's a real abuse of trust here and the victims were children who were particularly vulnerable," Judge John North told the NSW District Court on Monday, sentencing Montoya to two years' jail.

Montoya pleaded guilty to producing child abuse material, accessing child pornography and possessing child abuse material.

He sobbed and wiped away tears as he listened to the judge describe his crimes, including possessing 507 child pornography images and four videos, which showed children aged between two and 14 in sexual poses or engaged in sexual acts.

Judge North said that, while there was no evidence he shared or sold any of the images with anyone else, Montoya's crimes were serious.

"It's clear that by accessing and possessing child pornography, the offender has taken advantage of the sexual exploitation of children.

"Children have suffered and will continue to suffer, their image is captured forever. This is not a victimless crime.

"Those who possess such material help continue a market for child exploitation."

Montoya also admitted to inciting a woman to send him sexual photographs of her 15-year-old daughter.

In a series of messages in September 2015, Montoya asked the woman to pose with the girl naked or in their underwear.

One message read: "The thought of you both just over excites me ... You are everything to me!!! Sexy Sexy Sexy!!!"

Judge North said he accepted that Montoya was remorseful, and had since realised the gravity of his crimes.

"He said 'I'm beside myself with guilt.' "

But the judge said Montoya needed to continue treatment for paedophillic disorder after he is released from custody.

Judge North ordered he be released in January 2019 under the supervision of Community Corrections and adhere to strict conditions.

With tears on his cheeks, Montoya put his hands into a prayer pose, kissed them and gestured at his family as he was led down to the cells.