A forced return to remote learning for a Lower Hutt high school after the discovery of mould last month is "not surprising", says the New Zealand Principals' Federation president.
Eight teaching spaces at Hutt Valley High School were isolated on March 25 after "unsafe levels of mould" were identified in a block of classrooms.
The school said it had since been found in "other parts of the school".
Classes were relocated to the hall and library, and the school advised earlier this week senior students would learn remotely on a rostered basis next term, with year 12 and 13 attending two and a half days a week.
New Zealand Principals' Federation president Perry Rush said the situation reflected a wider struggle for some schools to maintain and modernise ageing buildings.
"Schools that aren't in high role growth areas, we're seeing these schools tolerating the state of their buildings.
"I think we're seeing some schools with very substantive challenges that have insufficient funds and they are simply tolerating that situation, they are not getting the service they need to modernise at pace.
"I think we're seeing that at Hutt Valley High School, a school that has called out for more funding for a long period of time."
He said he was surprised the mould was only recently picked up through remediation work on the block.
"There are significant warning signals for schools and school buildings that have features of being leaky, and it sounds like this particular block at Hutt Valley High School has all those warning bells.
"It sounds to me like the full design, the nature of the design, the nature of the cold spaces, the lack of ventilation, these are very common features of leaky buildings that should have been picked up well before now."
He said the return to remote learning for some students was "hugely disappointing".
"The real message here is that there needs to be quick remedy and a lasting solution that future proofs the school for the next 50 – 80 years.
"I must not just be a band-aid, it must be done well."
Hutt Valley High School acting principal Denise Johnson has also been approached for comment.
Ministry of Education property delivery associate deputy secretary Scott Evans said all schools received maintenance funding "for the upkeep and development of their property".
"However on occasion, building deterioration can accelerate and manifest in problems such as mould.
"Where we are made aware of this, or any other urgent health and safety issue, we immediately provide schools with extra support."
Evans said the ministry appreciated the situation was an "unsettling time for the school community" and was looking at short and long-term options.
"In the short term we're looking for leased accommodation the school can use, and have discussed a number of options with the school already.
"For longer term options we are considering include getting relocatables on to the site, and replacing the block."
It was also carrying out further air testing at other parts of the school as a precaution.
It was aware the school community had concerns about their level of engagement with the ministry, Evans said.
"We are having constructive meetings with the school that are focused on delivering a solution.
"Once that work is completed we will be reviewing our engagement with the school on their property and maintenance funding over past years, to identify where we could have worked better together and to strengthen our relationship into the future."