The abuser was arrested last year and has been held in custody since them. He was granted name suppression, which lapsed today after his guilty plea.
The plea also means the details of his offending, also suppressed, can now be published.
The name of the school where Burrett worked remains suppressed, as well as the name of a bus company that employed him as a driver.
Court News reported that at today's hearing Crown prosecutor Deirdre Elsmore told Justice Cameron Mander that Burrett was employed as a school caretaker from the beginning of 2013.
Alongside that job he was also employed as a bus driver transporting special needs pupils from their homes to school.
She said all of the pupils he drove attended primary school and had intellectual disabilities. Many had difficulty communicating.
According to Court News Burrett "repeatedly invited one girl aged between eight and 10 years into his underground shed on the school grounds where he would talk to her about "adult stuff" and told her not to tell anybody".
One day he met her as she was walking to school and "hugged her, kissed her on the cheek, and told her to be good in class".
The girl told police she thought it "weird and gross".
On many occasions Burrett took two girls into the shed and touched them and carried out indecent acts. They were nine and 10 at the time.
Burrett used a vibrator on one child and showed two others pornographic videos during the school breaks.
One girl said she was raped and she described the abuse as "painful and gross".
Burrett also recorded himself committing indecencies and then played the recording back to the girls, Court News reported.
He committed indecencies during a "dice game" with two girls, and recorded them on video before playing the recording to them.
Mrs Elsmore also told the court Burrett threatened one girl aged between five and seven. He indecently assaulted her and then said if she told anyone he would "smash" her.
She carried on to detail other offending including Burrett telling one child "about sexual matters, and what sexual things he did with his wife".
Some children were strapped to a chair during the abuse and others watched their classmates being abused in the shed.
Burrett was remanded in custody and will appear in the High Court for sentencing in April.