Auckland girl's school Marist College has 47 confirmed and probable cases of Covid-19.
It is the biggest cluster of infection being tracked by health authorities.
The board chairperson Stephen Dallow says the confirmed cases include teachers, students and adults within the community.
The entire school of about 750 students, as well as staff, is classed as close contacts and they have been asked to keep to strict isolation rules.
- If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs) or call your GP - don't show up at a medical centre
Sevety-six new cases of the virus were confirmed around New Zealand today, bringing the total to 589.