Mr Kaua said 76 per cent of the school's students were of Māori descent.
"And of those students, 90 per cent are from the awa - so then it's also about the importance of the Whanganui mita [dialect]."
Mr Kaua said the board and school management would work through the logistics of how compulsory te reo would work.
"Our year 9s do English, science, maths, social science and health and PE - those are all compulsory. Then they choose four options.
"So logistically we haven't got our heads around how we're going to organise this - but it definitely needs to happen."
Mr Kaua said he hoped giving all students the opportunity to learn an official language of Aotearoa-New Zealand would ignite an interest to pursue it at other levels.
"We are not only talking about an interest in te reo, we are also very keen to build on our 'place-based' thematic unit introduced into the year 9 programme two years ago.
"The theme is centred around a well known local Whakatauki, 'From the Mountains to the Sea', and overlaying this learning with te reo and tikanga of the iwi enhances the sense of belonging and being a part of this wonderful place."
Mr Kaua believes every student should be given the opportunity to learn the language of their country, in the dialect of their iwi.
Board chair Mark Pirikahu said te reo Māori had been "hidden" for too long, and he'd like to see that change.
"So for us here at Whanganui City College it's about asking ourselves, where do we see te reo Māori fitting in to our school? And how are we going to lift that up schoolwide, so that te reo Māori is no longer a hidden subject?"
Mr Pirikahu said te reo Māori should not be seen as secondary to English, but should have equal status.
He said his grandparents' generation were punished at school for speaking te reo Māori.
"But it's different these days - we have all these opportunities to make changes for the betterment of our school, and of the reo."
Mr Kaua said the roll-out would involve support from local iwi and kura kaupapa Māori, whom he knew would gladly assist with resources and knowledge.
"We, in turn, support them with resources that we have to enhance the learning of their students. So it's a reciprocal relationship and we are all after the same thing - success in learning and being proud of our heritage and where we are from."
Mr Kaua said he believed every New Zealander should learn at least basic te reo Māori.
"It's an official language of our country, and it should be treated as such."
