UPDATED: 4.03PM The shocking case of child rapist school caretaker Robert Burrett has prompted a Ministry of Education investigation into whether all school staff should be subject to the same mandatory reporting that applies to teachers and principals.

School bus driver and caretaker Burrett was today (Tuesday) sentenced to 19-and-a-half years in jail with a minimum non-parole period of 10 years at the High Court at Christchurch.

The 64-year-old grandfather admitted 21 abuse charges relating to 12 young victims, including rape, sodomy, forced oral sex, indecent assaults, video-taping of the offending, and watching pornography, often in his underground caretaker's shed.

Education Minister Hekia Parata today confirmed that the Burrett case has prompted her to ask the ministry and Education Council to investigate extending their powers to all people who work with children in schools.

However, she has stopped short of calling for a full inquiry into how Burrett came to work with children, despite having been forced from two schools in the North Island as principal and deputy principal after complaints about his incompetent and concerning teaching methods.

"I am assured from the work that the ministry has done that they have received no allegations of sexual impropriety in respect of this person," Ms Parata said.

"The first time that it occurred was on March 23, 2015 - that’s when his employer, the bus service provider - advised the ministry and that afternoon the process kicked in."

The current system, Ms Parata stressed, meant that it's left to schools to decide who they employ, leaving their boards accountable for employment decisions.

All professions do their best to keep schools and early childhood learning centres safe, she said, adding that the vast majority of people employed at schools are highly trustworthy.

However, people like Burrett are an “exception” and ones that the system needs to pick up on.

“What we have to got to do is make sure we are alert to any possibility that this impropriety ... is identified and reported early," Ms Parata said.

"This has been concerning for all of us and I think it has alerted all school boards and principals to take every care."

New provisions for the Education Council reporting means it is now mandatory for schools to report any teacher or principal who has resigned, left under a cloud, or who been sacked, Ms Parata said.

The Vulnerable Children Act 2014 also means that people working with young children must go through a police vetting process.

"We have strengthened the system along the chain," said the minister.

"I feel very sad for these children and their families. Today doesn't undo the harm but I hope it brings some measure of comfort to them."

A large crowd packed the public gallery to hear the harrowing victim impact statement and police summary of facts.

It tells how Burrett, who the Herald revealed had been forced from two schools in the North Island as principal and deputy principal after complaints about his incompetent and concerning teaching methods, preyed on young girls aged between 5 and 12.

He taught for more than 40 years in schools across the country, before becoming a tutor, relief teacher and bus driver.

Burrett, who has two drink driving convictions in 2001 and 2007, was employed as a part-time caretaker at a Canterbury school from the beginning of 2013, after having been a casual relief teacher.

Alongside that job, he was also employed as a bus driver transporting special needs pupils from their homes to school.

All of the pupils he drove attended primary school and had some form of disability that affected either their communication and/or physical and mental functioning.

Between February 1, 2013, and February 23, 2015, invited a girl, then aged between 8 and 10, on multiple occasions to his "underground" caretaker's shed in the school grounds where he had installed curtains and a lock.

He gave the girl chocolate and lollies and talked with her about "adult stuff" and not to tell anybody.

As she would climb the stairs to leave the shed, Burrett would touch her on the bottom, the police summary says.

On another occasion, Burrett approached the girl in a park.

"He hugged [the girl], patted her on the bottom and asked if she wanted to come with him in his vans to do some jobs at school. [The girl] ran to a friend's house nearby," the summary says.

Between February 1, 2013, and February 23, 2015, Burrett approached another girl as she walked to school.

He hugged her, kissed her on the cheek, and said, 'Hi, darling. Be good in class', which the girl thought was "weird" and "gross" and ran to class.

Around the same time, Burrett took two girls aged 9 and 10 into the shed and abused them.

Burrett showed them pornographic videos, played sick dice games with them, and filmed the abuse before replaying it to them.

Another girl aged between 10-12 says she was raped "most days during morning teas or lunch time".

Other young disabled girls told police how they were sexually assaulted while Burrett transported them to and from school. Burrett told them they had to keep it a "secret".

On March 25 last year, police raided his house and found a computer with hardcore child pornography on it.

The mother of young victims told Burrett in court today that his crimes had left her feeling like a useless parent, blaming herself for his offending.

The family, she said, feels "betrayed in the worst possible way" by someone they thought they could trust.

Her daughters are more suspicious now, affecting how they trust people, and are scared that the abuse will happen to them again.

The offending has affected the mother's relationship with her daughters.

"I hate you and hate what you have done to my daughters," she said.

The mother, holding back tears, told Burrett in the dock that she felt "disgusted" and "sickened", as well as angry and frightened that it could impact her "traumatised" daughters in the future.

She hoped no child is ever allowed near him again.

Burrett "groomed and manipulated" children in order to engage in sexual activity with them, Justice Gerald Nation said.

Burrett was a paedophile, the judge said, who was not only attracted to children but allowed himself sexual gratification from them in circumstances he must've known was morally repugnant generally and with his own family.

The judge acknowledged the devastating effect his offending has had on the families and parents, and the gross breach of trust which has had devastating consequences for everyone involved.

All families had been suffering their own particular demands and stresses at the time of the offending, he said.

One family was going through a devastating family situation which Burrett had known about and still abuse their child, the court heard.

One report before the courts said that one child had become "disillusioned with the world" and did not trust the intentions of adults now.

Parents now feel like they have let their children down, Justice Nation said.

While the instinctive reaction of most people would be that no sentence would be too harsh and that Burrett should spend the rest of his life in prison, the judge said he was bound by law.

In sentencing Burrett, Justice Nation said that unless he made significant change to his thinking, it was unlikely that the Parole Board would grant him parole.

If he didn't change, he'd have to serve the whole of his sentence and would be very elderly on his release.

Defence counsel Rupert Glover said it had been "a very difficult case".

Burrett initially pleaded not guilty in April last year but since then had slowly come to grasp the gravity of his offending, Mr Glover said.

By last December, a psychiatric report found Burrett had significant psycho-sexual disturbance.

Reading the victim impact statements had acted as an epiphany for Burrett, Mr Glover said, making him suddenly realise what he'd done.

He was very remorseful and knew that he required treatment, the lawyer added.

Mr Glover reiterated outside court that Burrett was "very remorseful" and "still struggling to come to grips" with what he had done.

"It occurred to him slowly as time went on the gravity of what he had done and he understands that the harm was irreparable," he said.

The Ministry of Education earlier welcomed the length sentence imposed on Burrett.

“Burrett’s offending was abhorrent and cruel and one of the worst of its kind against children," Katrina Casey, the Ministry’s deputy secretary for sector enablement and support.

“We commend the police for their work in bringing Burrett to justice. This was a difficult and painstaking enquiry and one that required the utmost care towards the children involved.

“Our sympathy goes out to the children and their families."

The Ministry continues to support those affected and encouraged schools to contact it directly to discuss any further help and support if and when needed, Ms Casey added.

Robert Selwyn Burrett's sentence of 19-and-a-half years in jail, with a minimum non-parole period of 10 years, is one of the toughest ever handed down to a New Zealand rapist.

The lengthy sentence marks Burrett as one of New Zealand's worst ever sex offenders.

Other cases include: