Nearly every child now attends some form of early education before they start school. But cracks are starting to show in the system and children could be at risk.
Many early childhood centres are struggling to make ends meet and teachers say some are deliberately cutting corners that leave children in the care of too few adults.
Overall government funding has increased as enrolments rise, but the amount paid per-child has been frozen at times and has not increased in real terms for nearly 10 years.
Now, whistle-blowers warn that dangerous practices are putting children's safety and emotional well-being at risk.
Teachers have told RNZ News that some early childhood centres often operate with fewer teachers than the legally required minimum, and some provide poor supervision of large groups of children.
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Organisations representing early childhood services acknowledge poor practice is happening and say cracks are appearing in the sector because of years of government under-funding.
One teacher who spoke to RNZ News on condition of anonymity said she worked with children under the age of two in a large early childhood centre, which often failed to meet the minimum requirement of one teacher for every five children.
"More often than not we would be running at 35 children in a room that was licensed for 30, with five teachers," she said.
The woman said the centre's managers would count its van driver and cook as teaching staff, even though they were not in the room looking after the children.
She said the situation was not safe.
"Our teachers were highly stressed. We were always living in flight mode and if our teachers are living in flight mode just imagine what is happening to our children every day," she said.
Despite the shortcomings in the under-two-year-olds' area, the teacher said she and her colleagues often kept children there beyond the age of two because it was safer than the next room, which had as many as 50 children over the age of two.
"Often you'd look over and the teachers weren't watching the children. There were ropes going around children's necks, there were children breaking bones, there were children receiving head injuries and a lot of the time these things weren't being documented by staff. It was really horrific to watch."
The teacher said when she complained about the situation, she was forced out of her job.
She said teachers needed to know they could complain to the Education Ministry and the Education Review Office when they saw bad practice.
Another woman who agreed to talk to Insight on condition of anonymity said she too was forced from her job when she complained about a teacher who was abusing children.
"They're grabbing children to take them to the toilet, they're not respecting them, they're holding them down while they're sleeping, they're humiliating them," she said.
The woman said the children at the centre were clearly upset by the mistreatment.
"There was one child especially [who] would come to me and ask where this particular teacher was and she would avoid her. You have children who were just wetting themselves because they didn't want this particular teacher to take them to the bathroom or to take them for a nap," she said.
The teacher says the centre's owner took no action over her complaints and as far as she was aware the abusive teacher was still working at the centre in March this year.
The organiser of the Teachers' Advocacy Group, a support network for early childhood teachers, Susan Bates, said such stories were not uncommon, but most teachers were too scared to speak out or lodge formal complaints.
"Some of these things are absolutely common. People are told that they're out of ratio and that's just how it is, you just live with that. As long as the paperwork looks fine when it goes off to the head office or to whoever," she said.
The chief executive of Child Forum, Sarah Alexander, said similar complaints were raised in its surveys of early childhood teachers in 2015 and 2017
"A consistent theme that comes out from those surveys is concerns about groups sizes, about having too many children within an early childhood service environment for teachers to cope with, concerns about noise level, concerns about stress that teachers are experiencing, concerns about funding - not just about the amount of funding, but about the funding not reaching children and not being spent on the children," she said.
Dr Alexander said about a quarter of respondents reported the quality of the early childhood service where they worked was so poor they would not let their own children attend it.
She said it appeared some services did not understand the rules for maintaining teacher-child ratios and were counting staff who were not working directly with children.
Education Review Office figures indicated there had been a slump in quality in recent years.
In the 2016-17 financial year, 1.5 percent of reviews discovered sufficiently serious concerns to warrant another review within a year - double the figure two years earlier.
During the same period, the percentage of reviews resulting in the next level of scrutiny, a return visit within two-years, climbed from 8.4 percent to 9.6 percent.
And the percentage of reviews resulting in the gold star standard of a review in four years time dropped from 14 percent to 11.4 percent.
The chief review officer, Nicholas Pole, said common problems in badly performing services included poor leadership and management, poor teaching, and poor appraisal and development of staff.
"ERO's greatest concerns in terms of ownership structures are with single operator services and those operating a small number of services, where approximately one in five have been identified as being of concern," Mr Pole said.
"A paradox here is that these small operators are also likely to operate some of our best services. Large providers (those operating 20 or more licenced services) operate few services of concern, however these equally fail to be outstanding in their performance," he said.
Both the Early Childhood Council, which represented about 1200 early childhood services, and Te Rito Maioha Early Childhod New Zealand, which represented about 450 services, agreed there were problems in the sector.
They said many centres were struggling because of a shortage of qualified teachers and because the government's per-child subsidies had not increased in real terms since 2008.
Education Minister Chris Hipkins said he was still taking stock of the sector.
A lack of government funding and rapid increases in enrolments had put early childhood services under strain and there was wide variation in quality.
Mr Hipkins said the Education Review Office and the Education Ministry were good at identifying problems, but they needed new ways of intervening in poor-quality services.
"The ability to intervene at that top level, at the governance management level is much more difficult in early childhood than it is in school sector," he said.
The Education Ministry's deputy secretary sector enablement and support, Katrina Casey, said the teacher child ratios were a legal requirement.
"A breach of those requirements would be totally unacceptable," Ms Casey said.
She said anyone with information about a specific service falsifying records or breaching its licence in any other way should provide the ministry with that information.
"We will investigate. Any service that is found to have breached its legal requirements is putting its licence at risk.
"We can, and do, close down services".