"We didn't think it wouldn't happen but the concern for us was how long it might take given that a different funding model would be put in place."
Under a PPP arrangement, a private funder is responsible for the building and maintenance over a long period and the Government makes a regular payment to it.
Rob Giller, Ministry of Education acting head of Education Infrastructure Service, said the redevelopment would go ahead as planned with construction starting in 2019 and completion in 2022.
"The delivery approach for new schools that do not have signed PPP contracts, including Whangarei Boys', will be determined through the upcoming Budget process," he said.
Mrs Gilbert-Smith said as part of the upgrade some classrooms would be refurbished, some demolished and rebuilt.
She said the upgrade was "hugely important" because spaces were needed that allowed for diversity in curriculum.
"We've got a lot of temporary classrooms on site that were never meant to be permanent and have become permanent over time ... We have had issues with leaky buildings and we've had earthquake strengthening issues.
"So it will be amazing for the students now and into the future to have facilities that are in line with other schools. For me it's quite amazing that despite what I would describe as sub-par facilities our boys are hugely successful."
Mrs Gilbert-Smith said the education brief, which talks about how the school wants to teach and what spaces are needed to achieve that, and cultural narrative, which provides a historical narrative to assist in informing the design of the rebuild, were completed between the time of the announcement and January.
The next step would be to work with an architect and Mrs Gilbert-Smith anticipated that process would start in Term 2.