Mathematics tutor Quy Huy Hoang enjoyed such confidence from the Sydney families who hired him that they referred their friends for lessons, and installed locks and blinds at his urging. But out of sight, the ‘monster’ was haunting the children he was entrusted with teaching.

The 68-year-old showed no visible emotion in the dock of Sydney District Court on Friday as he was handed a 24-year jail term for sexual crimes against five children to whom he gave private lessons between 2007 and 2014.

His victims were aged as young as three and were subjected to a barrage of meticulously planned sexual and indecent assaults.

For some of the children these attacks happened weekly.

Though Friday’s decision fell short of the life prosecutors had urged Judge Kate Traill to hand down, the hefty non-parole period means Hoang – known as ‘Mr Peter’ to his victims and their families – will not walk free from jail until he is at least 85.

‘In my view, the offender is a sexual predator who took advantage of his high position of trust as a teacher and elder of the Vietnamese community, and abused that trust to sexually abuse very young children,’ Judge Traill said on Friday.

‘To add insult to injury, the offender took money from (the complainants’ parents) whilst he was sexually assaulting the children.’

Judge Traill, one of two specialist District Court judges appointed last year to hear child sexual assault cases across the state, said the offender had shown no remorse and she believed he still posed a danger to the community.

She told how Hoang had convinced one mother that she should put blinds on windows, install locks on doors and use particular tables and chairs – all under the guise of improving her children’s school marks.

But Judge Traill said she was satisfied Hoang’s real intention was to fashion the children’s home into a place where he could abuse the children uninterrupted, so that ‘as one walked into the room they would not see his hands’ fondling the children.

The mother she spoke of later told a psychologist: ‘I created a perfect haven for him to abuse my babies.’

Another mother – whose eldest daughter had recently died in a car crash, and who had lost her husband to cancer shortly before meeting Hoang – could not afford the tutor’s services, and believed it was kindness that motivated him to offer free lessons.

A victim impact statement tendered to the court details one mother’s anguish at allowing Hoang into her home.

‘All my children still refuse to sleep in their bedrooms,’ she said.

‘The room is left abandoned and my children have told me numerous times that the room is haunted and that bad things happen there’.’

She said she cried in silence so her children do not hear her.

‘Mr Peter has broken my children’s childhood, stolen their innocence, blacked their hearts and stolen their smiles,’ the woman said.

‘What a monster he is.’

Outside court, Detective Chief Inspector Peter Yeomans from the Child Abuse Squad commended the courage of the child victims in shining a light on Hoang’s ‘diabolical’ crimes.

‘The victims in this matter exhibited extraordinary bravery for their young age,’ Insp Yeomans said. ‘It was their actions that stopped this offender reoffending.