Professor Macartney's investigation, commissioned by NSW Health and the Education Department, tracked all 18 cases of COVID-19 among students and teachers across 15 schools. "We have seen an extraordinarily low rate of transmissions in schools," Professor Macartney said. Nine students and nine staff members were COVID-positive, and all 18 cases had the opportunity to transmit the virus to others within their schools, the report published on Sunday found. “Our investigation found no evidence of children infecting teachers,” the investigation – the largest of its kind internationally – said. “It is notable that half of the initial cases that occurred in schools were in staff."

Loading Among 863 close contacts of the 18 initial cases - 735 students and 128 staff - the investigators found just two additional COVID-positive cases: one primary student and one high school student. The findings back advice from Australia's health protection principal committee, which has not wavered from its recommendation that schools stay open and can be kept safe in the face of simmering tensions between the teachers unions and governments. On Friday Prime Minister Scott Morrison said the risk to teachers "is not in the classroom - their risk is in the staff room". The report follows Premier Gladys Berejiklian's announcement that all government students, including those in year 12, would be asked to attend school for one day a week from May 11, and that this would slowly increase until term 3, when all students would attend full-time.

Loading Education Minister Sarah Mitchell said: "We know that COVID-19 has created some anxiety for parents, teachers and school staff. However, the findings in this report confirm existing health advice that schools remain open and are safe for students to return. "Our managed return to school provides an orderly pathway to return students to the classroom and allows for additional measures for teachers and parents." Professor Macartney's team traced every case of COVID-19 in schools since the first confirmed case in a year 11 student at Epping Boys High School in early March. The transmission of coronavirus among students seems to be considerably less than for other respiratory illnesses.

Children have been dubbed super-spreaders of influenza, but virus and antibody testing suggests children are not the primary drivers of coronavirus transmissions. Loading International studies show low rates of COVID-19 in children, and NSW Health data shows school-aged children account for 1.6 per cent of all COVID-19 cases in the state despite being roughly 16 per cent of the population. Professor Mary-Louise McLaws, an epidemiologist at the University of NSW, said: “We have a vague idea that children have less receptor sites for the virus. We don't understand why some kids get it and the majority don't, but if they were real drivers, you'd see a very different epidemic curve." Across 10 high schools, there were 12 confirmed cases (eight students and four staff) – 596 students and 97 staff were identified as close contacts, defined as a person who has been in face-to-face contact for at least 15 minutes or in the same room for two hours with a case.

The researchers performed nasal or throat swabs on one-third of these contacts. All were negative. Of the 75 close contacts that underwent blood tests, only one student had antibodies for COVID-19. Loading Replay Replay video Play video Play video There were six confirmed cases in primary schools (one student and five staff), with 137 students and 31 staff close contacts. One-third were swabbed and 21 close contacts of this secondary case were blood-tested. Just one student tested positive. Professor Macartney said they are confident they did not miss anyone who was ill with COVID-19 and had tested a representative sample. Health Minister Brad Hazzard said NSW Health experts are doing an exceptional job supporting schools during the pandemic.