Otago Girls High School principal Jan Anderson said anyone with a sniffle or a sneeze would be sent home during the next few days, in an effort to make sure they were fit and healthy by the time they returned from their two-week holiday, which begins at the end of this week.
"Schools in Dunedin are hoping to minimise the effects of flu and swine flu by using the holiday. We've got that lucky break where the pupils aren't gathered together spreading any flu germs that they may be carrying."
Kaikorai Valley College principal and Otago Secondary Principals Association chairman Philip Craigie said there had been a "huge" amount of sickness at the school in the past week.
The school was also one of two Dunedin schools affected by swine flu. One teacher and one pupil were confirmed with the virus, influenza A (H1N1). A pupil at Logan Park High School Services Academy has also tested positive for swine flu.
Mr Craigie said while it took up to two weeks to fully recover from winter flus, many pupils returned to school too early, with coughs and runny noses, only to reinfect their classmates.
"We've been saying to pupils, if they are sick, stay at home. But some have come to school anyway, who probably shouldn't have."
As well as sending sick pupils and staff home, Mr Craigie said the school was not holding any school assemblies or parent teacher nights this week, and some school trips had been cancelled. They were some of the strategies aimed at keeping large groups of people from congregating in small and confined places, he said.
There has been no increase on the three confirmed cases of swine flu in Dunedin. Nationally there are now more than 650 confirmed cases, mostly in Auckland, Wellington and Canterbury.
