Freeman Catholic College at Bonnyrigg Heights and Mary Immaculate Catholic Primary in Bossley Park will return to remote learning for all students until August 10 after additional positive COVID-19 tests.
Sydney Catholic Schools confirmed additional cases of COVID-19 at the schools which were closed on Monday and Tuesday after two positive cases last week.
"Both students have been in isolation since the weekend and neither have attended the re-opening of the school today [Wednesday]," the statement read.
"Neither student has been in attendance since the sites underwent their deep clean.
"Given the online learning program was successfully administered in both schools in Term 2, this will ensure continuity of learning for all students. The health and safety of our students, staff and community as well as quality teaching and learning are our ultimate priority.
"We continue to work closely with the NSW Health contact tracing team."
Fairfield mayor Frank Carbone said the students who tested positive are in Year 9 and in Year 12 at Freeman Catholic College.
"Both students are well but showing minor symptoms," he wrote in a post on Facebook.
"NSW Health will now be contacting families to inform some students that they are 'close contacts' and that they will have to self-isolate. If you are not contacted by NSW Health you are not deemed to be a close contact.
"Other members of the school community are asked to be alert and get tested if any symptoms occur.
"I have also been informed that positive cases have also been found in several other schools, including one at Mary Immaculate Catholic Primary which will also close until August 10."
School staff will be on site and the schools will be open for students of essential service workers until face-to-face teaching resumes.
NSW Health recorded 19 coronavirus cases on Wednesday two of which involved people in hotel quarantine and 10 others connected to the Thai Rock restaurant in Wetherill Park taking the size of that cluster to 85.
There has also been a confirmed case of COVID-19 at EverLearn Preschool in Prestons.
"I am advised that the preschool will be closed so that NSW Health can conduct contact tracing and the preschool can be deep cleaned," Holsworthy MP Melanie Gibons wrote on Facebook.