A Sydney high school and a Catholic primary school have been closed for deep cleaning and contact tracing as NSW records 13 new cases of COVID-19.
The NSW Education Department on Friday said Ryde Secondary College, in the city's northwest, will be closed after a staff member tested positive.
Staff and around 1000 students at the co-educational school have been asked to stay home while the contact tracing process begins and the school is deep cleaned.
St Gertrude's in Sydney's west is also closed on Friday after a student was diagnosed.
A spokeswoman said the school had around 650 students from Kindergarten to Year 6, and 50 staff who have been advised to isolate at home and monitor for symptoms.
Riverstone High School, Wyndham College and Schofields Public School will reopen on Friday after COVID-positive cases previously attended school.
NSW recorded 13 new COVID-19 cases in the 24 hours to 8pm on Thursday from more than 30,000 tests, with just one in a returned traveller in hotel quarantine.
Six new cases were linked to the Sydney CBD cluster associated with the gym at City Tattersalls club, with that cluster now numbering 14 people.
NSW Health says anyone who attended the City Tattersalls gym between 8am and 2pm on 19, 21, 23 or 24 August should get tested and isolate at home for 14 days.
The club has again been closed for cleaning.
Premier Gladys Berejiklian warned residents to remain on high alert as spring nears.
"Every week we are detecting unknown sources, even though it's in relatively low numbers, but every week those numbers accumulate," she told reporters on Friday.
"As the weather warms up and as spring is upon us we just want to make sure that everybody thinks about their movement outdoors and is COVID-safe. We appreciate that a lot of the places people normally flock to will be very busy on the weekend."
Holy Name Catholic Church at Wahroonga was also shut as a precaution, after a parishioner who attended church on Sunday 23 August tested positive.
People in Australia must stay at least 1.5 metres away from others. Check your state’s restrictions on gathering limits.
If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080.
