Spotswood College has temporarily closed its gym after rot was found in its beams.
Principal Mark Bowden said an assessment by the Ministry of Education found further investigations were needed.
"It's not condemned at this point. But they've said to keep it closed until the investigation tells us exactly where we are at with it," he said.
Pupils are using outdoor courts, empty rooms and also the school hall for PE and various sporting activities.
Four years ago, the school applied for funding to tear down three 50-year-old wooden buildings and replace them with two modern learning spaces.
Upgrades would cost the school about $15 million.
But if repair works were needed for the gym, the school will have to divert money tucked away for upgrades to repair the building.
Bowden said school buildings were investigated after the Christchurch earthquakes to make sure they were earthquake resilient.
"Then out of the blue, this has come up, so we'll just go with the flow while the investigation is being completed," he said.
Bowden said it had been "pretty jolly frustrating" and they wanted the problem resolved quickly.
He said the ministry had been helpful in the latest situation but the school also felt it had been struggling to get "some progress" for its buildings.
"I have spoken with MP Jonathan Young and he has undertaken to advocate for us," he said.
Bowden said the school's board of trustees is working hard to set a strategic property plan to get the school "completely modernised" over a period of time.
MOE spokeswoman Kim Shannon said the ministry was now seeking engineering advice to determine the severity of the structural issues.
It was also working with the school to consider alternative options, should the building be "unavailable for any length of time".
Spotswood is not alone in its predicament.
Primary schools Ramanui and Hawera, both in South Taranaki, are faced with borer-infested buildings.
Ramanui will have to tear down its 61-year-old borer-infested main building while Hawera has temporarily closed off its school hall.
- Taranaki Daily News
What's your expectation of former tropical cyclone Pam?Related story: Cyclone Pam hits New Zealand
Get Taranaki's frequent news and sport updates
Get your mid week news fix
Get your South Taranaki news online