The Christchurch primary school caretaker who raped and sexually assaulted 12 young girls has been labelled a "cunning predator" by a primary principal.
The principal says his offending was pre-mediated and calculated and warns it's difficult to protect children against sexual offenders with clean records.
It was the caretaker's shed of horrors where 64-year-old Robert Selwyn Burrett took 12 girls as young as five.
Yesterday he pleaded guilty to 21 charges, including rape and sexual assault.
Burrett had installed curtains and a lock and some of the girls had mental or physical disabilities.
"This is a predator. He has obviously set up – he's known that these children are vulnerable. He's known that they'd have difficulty reporting and that's what's allowed him to get away with this. It's absolutely appalling," says Rob Callaghan from the Canterbury Primary Principals' Association.
Mr Callaghan says he believes the Christchurch school did everything in its power to screen Burrett before employing him as a caretaker, bus driver and relief teacher.
"What makes it difficult is if you have someone who is setting out to commit a crime like this then it may not matter what systems you put in place. If a person is determined, they will find a way," he says.
The Education Council, which is responsible for ensuring teachers are safe to be around children, says its screening process is robust. It says it will look into whether Burrett may have offended in previous positions.
"The Education Council will be talking to police about Mr Burrett and we'll also be talking to the Ministry of Education about his past behaviour," says Education Council managing teacher practice Andrew Greig.
And while it's too little too late for his victims, Burrett has been struck off the council's register and will never be allowed to teach again.