The student at an Auckland primary school previously considered a close contact has tested positive for COVID-19.
Auckland Regional Public Health Service (ARPHS) says the student from Henderson North School is now in self-isolation and they were not infectious while they attended school.
There are no close contacts for the student, according to an investigation by ARPHS, and the risk to other students or staff is very low. The school remains open.
"The student and their family continue to self-isolate and their health and wellbeing is being monitored by public health," ARPHS says.
It warns people that there are cases in the local community so residents should be vigilant of symptoms of COVID-19, including a cough, runny nose or sore throat. Anyone with those symptoms should ring Healthline or their GP for advice.
The school says it understands "if you wish to keep your children at home but please be good enough to inform us".
The new case is the second student at a west Auckland school to test positive in recent days after a student at the nearby St Dominic's Catholic College became infected.
On Tuesday, ARPHS wrote to parents to say a student at Henderson North School had been identified as being a close contact of someone with COVID-19.
Following news of the St Dominic's Catholic College case, the Ministry of Health began working with the school to test all staff and students in the community. On Thursday, the school's deep clean had been completed and testing was underway.
"Testers have been supplied with a surveillance code for testing of asymptomatic members of the school community so it can keep track of the numbers," the Ministry of Health said.
"As at 11am today, labs had registered 561 tests against this code. There will also have been additional tests where the person did not specify they were connected with St Dominic’s.
"Staff and students have been provided with access to two dedicated testing centres not open to the general public. This means they can be tested without long waits and the results can be processed as quickly as possible – tests from these sites are prioritised at laboratories."
Most of the students were considered casual contacts and were being tested as a precaution.
A health policy service in Henderson also had an employee test positive earlier this week.
Meanwhile, the Blockhouse Bay school of Glenavon also had a case confirmed earlier this week. The student didn't attend school during their infectious period and are now isolating with their family.