Pools of sewage wastewater on a Hawke's Bay school playing field is "Third World" and unhealthy, parents say.
But Bryony Lovatt, acting principal of Eskdale School in Napier, said the issue had been well-managed and no children were getting sick.
The Hawke's Bay District Health Board, Hawke's Bay Regional Council and Ministry of Education were all aware of the situation, that has been present since winter 2011, and were happy with the way the Year 1-8 school was handling it.
A parent, who wished to remain anonymous, contacted Hawke's Bay Today yesterday after walking into a "sinking bog" on an otherwise dry field at the school's cross country day last week.
"The children are playing in their own faeces like a Third World country," the parent said.
"We send our kids to school believing that the teachers and trustees have our kids best interests at heart but I do not believe for a moment that any ethical person could justify letting this happen. Yet here we are."
The area was roped off yesterday afternoon, but before this only red flag markings were present, including on school cross country day when children ran a course through the flagged area.
"On questioning my children, they know nothing about the sewer water, just that they have been told not to play around the flags due to the mud," the parent said.
"They said they still play in it where the teachers can't see them from the staffroom and gave a recent story about a 5-year-old that was playing in the 'mud' and the teachers had to shower him off."
Mrs Lovatt countered that there were no records of children getting sick, agencies had assured the school it was safe and she did not know of other parents who had raised issues.
"We have no knowledge of any children becoming sick due to children playing on the field," she said.
"We have taken precautions, we have now been instructed to keep the area roped off.
"We have worked very carefully with the council and had water tests done. I am quite confident that it is fine."
When asked if she would be okay with her own children playing on the field she said: "Yes I would, and I walk across it myself."
Hawke's Bay Regional Council compliance and harbours manager Bryce Lawrence said the problem arose not from the system, but the field itself.
Hundreds of metres of underground drip lines released controlled amounts of effluent into the ground at regular intervals, treating waste as it absorbed into the soil.
"There's no reason to believe there's anything wrong with the system, it's the disposal field," Mr Lawrence said.
A clay tablet, that was not known about at the time consents were granted by council, stopped this process and sent the waste to the surface.
"It appears that the disposal field was put on a site that when it was approved it wasn't identified there was a clay pan underneath, which means the wastewater can't be treated adequately because it is rising to the surface," he said.
The wastewater was not safe, he said.
"It is treated to a better quality than a septic tank but that doesn't mean it's safe," Mr Lawrence said.
A Hawke's Bay District Health Board spokeswoman said the board's Public Health service was aware of the issue and was working with the council, the school and the Ministry of Education.
"Public Health supports the regional council's advice to effectively cordon off the whole top field until a more effective solution is found," the spokeswoman said.
Mrs Lovatt said a new section in front of the school was awaiting resource consents to become the new disposal land.
"The ministry has bought a new section for us and that has been developed and we are waiting for consent to approve the wastewater being disposed around the edges of the new field."
Ministry of Education policy manager Jerome Sheppard confirmed the plan, and said: "There had to date been no breach of health or school regulations".