The $50 million upgrade of Whangārei Boys' High School could see 80 per cent of the school rebuilt on one of the fields.
In 2017 then Prime Minister Bill English and Nikki Kaye, who was Education Minister at the time, announced more than $50m would be invested in a major upgrade of the school, funded as a Public Private Partnership (PPP).
Whangārei Boys' High School principal Karen Gilbert-Smith said in the past three years a huge amount of work had looked at the type of classes they wanted as part of the upgrade - which is now being funded through a conventional construction contract as the coalition Government is no longer funding core public services through PPPs.
And a feasibility study was completed in February which showed it would be possible - and within budget - to rebuild 80 per cent of the school on the lower field.
"The feasibility study that we're now working with basically means that we'd carry on teaching in the spaces we have while the rebuild of the new school happens down on the field. Once that is complete we basically migrate into those buildings and demolish the existing ones."
The feasibility study also showed the whare, gymnasium, music and drama block, health and PE block and auto store buildings could be retained or refurbished, while the swimming pool, hard courts and caretaker's shed would also be retained.
Gilbert-Smith said an original master plan which suggested rebuilding the school around the existing site - a staged process which would take up to five years to complete - was rejected last year by the Ministry of Education's design review panel.
Rebuilding on the field would allow work to start in mid-2020 with expected completion in 2022.
"It's a once in a lifetime opportunity for us to create spaces that will meet the needs of the students now and into the future. It's hugely exciting and to be able to do that in a way that doesn't disrupt learning now is a win-win for everybody."
Gilbert-Smith said the next step would be to complete all tender documents to appoint relevant high-level contractors - from quantity surveyors through to architects - and once the design part of the project had started, the school would go into tendering for the build.
Kim Shannon, Ministry of Education head of education infrastructure service, said the ministry had been working closely with the school to develop an approach that maximises the positive benefit of the development and minimises disruption to the school during construction.
"We'll be working with the school on how to engage with the community on our plans and I expect that we will be communicating regularly as our plans develop."
Gilbert-Smith said the school would be consulting with the community throughout the process.