Glendowie Primary School's board of trustees says it could take up to two years to rebuild after an arson on Friday night.
Police are now leading the investigation into the fire that destroyed a block of classrooms at the school in east Auckland.
The board's chairperson Dawn Garbett says the school has a role of 650, of which about 150 mostly junior students are now without classrooms.
However, she says the board hopes to keep the school community together on one site, by putting up removable prefabs while the rebuilding takes place.
Ms Garbett says school representatives have already met with an emergency team from the Ministry of Education about what to do next, and they will meet again on Monday morning.