One-hundred-and-fifty close contacts of the student with coronavirus from Dunedin's Logan Park High School are being put in self-isolation.
They will all be tested within the next 24 hours and the school will now remain closed until after the weekend.
But Secretary of Education Iona Holsted said they're not expecting or planning for widespread school closures in New Zealand.
"We are planning for temporary closures as is happening at Logan Park, but as the World Health Organisation confirmed, the risk to children remains low and parents should continue to send their kids to school unless of course they are unwell," she told reporters on Wednesday.
Dunedin's mayor, meanwhile, hopes people take more notice of the messages given the seriousness of the two COVID-19 cases in the city.
Aaron Hawkins' comments follow a party of hundreds in the university student quarter.
University of Otago students on Tuesday held a large St Patrick's Day party just metres from Logan Park High School.
Hawkins said Dunedin has cancelled all public events likely to attract 100 or more.
"I would hope that people would take that guidance seriously and it isn't necessarily what we've seen in the last 24 hours in Dunedin."