Moriah College has become the second eastern Sydney school to close on Tuesday after a student tested positive for COVID-19.
The Queens Park school closed at 12.30pm on Tuesday after it learned one of its primary school students had tested positive for COVID-19.
Waverley College, which is located within 1.5 kilometres of Moriah, evacuated its senior school campus earlier in the day when parents of a year 7 student informed the school he had also been diagnosed with coronavirus.
An email to Moriah parents said it was "important that students go directly home".
"We wish to advise you that at 11:15am this morning, the College received confirmation from NSW Health, that a student in our school community has tested positive for COVID-19," the email said.
A Moriah College statement said the school received confirmation from NSW Health shortly before noon and activated its "COVID-19 Positive Diagnosis School Response Plan".
"In accordance with NSW Health advice, the College has closed whilst contact tracing is conducted, and the school is cleaned and sanitised," the statement said.
The student last attended the primary school on Thursday, May 21.
The Moriah campus will be closed until next Monday, but teaching and learning will continue through its online learning platforms.
Meanwhile, senior school students at Waverley College were picked up by parents or sent home on private school buses earlier on Tuesday.
"We wish to advise you that Waverley College has been informed by NSW Health that a student on the Senior Campus has tested positive for COVID-19," the school's message to parents said.
"As a precaution we are sending all senior students home effective immediately. Junior students should remain on the Junior campus, unless they are a sibling of a senior student."
A Waverley College spokeswoman said the school was co-operating with NSW Health after it learned of a possible coronavirus case in a year 7 student, who was not at the school on Tuesday.
"We immediately activated our critical response to get the boys home quickly and safely. We have been in touch with those students and staff members who were in close contact to the student, and we are awaiting further direction from NSW Health," she said.
The spokeswoman said the school had been preparing for a coronavirus outbreak "for months" and had procedures in place to deliver online schooling in the event of an extended closure.
"The school is very prepared for this, being [in] a coronavirus hotspot," she said.
Waverley College will be closed for deep cleaning before it is re-opened within two days. The spokeswoman said NSW Health would also re-test the student to confirm his positive diagnosis.
A different school student who was identified as a potential coronavirus case last week turned out to have returned a false positive test, NSW Health confirmed on Monday.
Premier Gladys Berejiklian warned parents to expect temporary school closures due to coronavirus cases as schools re-opened full-time this week.
St Ignatius College, Riverview was evacuated last week when a student tested positive.