Smells have been reported at Whenuapai School in west Auckland for years, public health officials say.
The primary school is moving children out of four classrooms into a new block these holidays after tests found chemical compounds were causing odours.
The school asked the national public health service northern environmental health team about it.
It told them it was an Auckland Council matter but they could support them raising it with a resource management team at council.
"This odour has been occurring for 25 years," a National Public Health Service spokesperson said.
The school said investigations were carrying on into the source of the smell.
RNZ asked the health service for more details around what it knew about the waste.
The service had advised the school to follow the recommendations it already had, to increase ventilation to avoid odour accumulating.
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