The man was of Indian ethnicity, with spiky hair, about 20 years of age in a blue sedan with the letter H as the first letter on the number plate, the school said.
"We have notified our local schools and all of our girls and discussed strategies to keep safe - walk in groups, always look out for especially the younger girls and don't hesitate to use iPhones to take photographs or call 111," the school said.
It was not providing further comment on the incident.
Lynda Reid, the principal at nearby private girls' school St Cuthbert's College, said Diocesan quickly alerted her school, which then spread the message among parents to be vigilant.
Police said the first reported incident occurred on Mauranui Ave about 4.30pm on Friday. A parent notified police today after 12pm.
A police spokeswoman said inquiries were being carried out into both reports.
Police want to hear from anyone who saw suspicious behaviour involving a "dark-skinned man" in a blue vehicle, possibly a sedan, in or around these locations over the past week.