Scores of students have been staying at home after whooping cough ripped through a Christchurch school.
Paparoa Street School principal Phil Harding says the infectious disease has caused chaos.
"Other students in that space started to drop like flies, and before we could turn round we had eight and then 10 and then 12 confirmed cases, and then probably quite another significant number of unconfirmed cases."
The school has been taking extra precautions.
"We've had our caretakers sanitise door handles and surfaces as a special extra precaution. We have regular cleaners but we send our day crew round every day before lunch wiping surface that children touch regularly."
Christchurch has one of the highest rates of whooping cough in the country. It is believed the first infected child in the current outbreak was not vaccinated.
Mr Harding is urging parents to get their children immunised, and sick or unvaccinated children are being encouraged to be kept at home. Nearly 120 students were kept home sick on one day last week.
"I think if a parent sees a child with a persistent cough and it's not stopping they should definitely visit their GP and they should start their child on a course of antibiotics, which is the treatment for whooping cough, and keep their immunisations up-to-date."
Mr Harding hopes the worst is over.