"This will enable us to connect with everyone who is a close or casual plus contact and for testing and follow up to occur."
The school said it is working closely with the Auckland Regional Public Health Service and the Ministry of Education to guide its response.
Close and casual contacts have already been contacted and are being given relevant advice by officials at the ARPHS.
"The remainder of the school are considered casual contacts," the note said.
"I realise this news will be worrying."
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Parents and staff who had any immediate health concerns were encouraged to call their family doctor or Healthline on 0800 358 5453 for Covid-related advice.
The news comes after news over the weekend that a teacher at Sacred Heart College tested positive for Covid.
The teacher was at school while potentially infectious and as a result, one student was considered a close contact. The other 30 students in his classes were fully vaccinated.
The student regarded as a close contact has had their first Pfizer jab. The teacher has also had their first jab.