It's been a bit of a roller-coaster weekend for Toronto father Yaser Nadaf, after Ontario's new asymptomatic testing for schools in COVID-19 hot spots turned up 19 new positive cases at his children's school.While his daughter and her Grade 3 class were cleared to return to school on Monday, his son's Grade 2 class must self-isolate for 14 days, even though the youngster himself was among those who tested negative.The weekend's testing blitz at Thorncliffe Park Public School — the first Toronto District School Board (TDSB) location selected for the voluntary testing pilot announced last week — saw 14 classes affected and sent home for two weeks. However, the rest of the school will remain open, according to direction from Toronto Public Health.Nadaf is rolling with it, saying he believes teachers and staff have been trying their best to maintain health and safety precautions and protocols."What can we do? This is going on everywhere in the world," he said. "They try their best, but at the same time they cannot prevent it completely."Testing asymptomatic students and staff is currently being offered at designated schools in Toronto, Peel and York regions and Ottawa — four Ontario regions with a high number of active COVID-19 cases.The goal is to improve tracking of the coronavirus and prevent transmission within schools, as well as to inform future public health decisions. While parents and health experts seem to be applauding the pilot, some are also highlighting shortcomings in how it's being rolled out.Over the weekend, testing also began in Ottawa at Manordale Public School, part of the Ottawa-Carleton District School Board. Amber Mammoletti, an occasional teacher working at two schools this fall, dropped by on Sunday to be tested with her son, Fynn."I think there's people walking around not realizing they have it — no symptoms — so it's just better to keep everyone safe: Get tested if you can and see what happens," she said.WATCH | How testing helped Cornell University become a model of COVID-19 prevention:School boards are working with local public health authorities to determine which schools to target over the next four weeks, but the expectation is that new positives will undoubtedly emerge, TDSB spokesperson Ryan Bird said."The 19 cases we've learned about over the weekend [at Thorncliffe Park PS] as a result of the testing is a concern, but it's not unexpected," he said Monday."While this information is concerning, it really is the information that our public health officials need to know, because it gives them a better snapshot of how many of those asymptomatic people are positive cases of COVID."Despite the batch of positive cases arising from this first weekend, Ontario Education Minister Stephen Lecce reiterated his assertion that "99.9 per cent of Ontario students are COVID-free" during a press briefing on Monday afternoon.Acknowledging that "we still have work to do" in tracking COVID-19 cases in communities, he characterized the new testing initiative as an extension of the existing safety measures his ministry had announced."The fact that hundreds of children, students and staff have gotten tested [at Thorncliffe Park PS] in conjunction with the local public health unit I think underscores that the plan in place is ... working hard to mitigate any further spread: identifying COVID cases, isolating them or moving them from the school, so we don't have spreaders within the school." 'Canaries in the coal mine'A targeted campaign of testing in schools — which in most neighbourhoods are considered trusted, known places — is a welcome tool that adds to the barometer of what's happening in the communities they're located in, said Dr. Zain Chagla, an infectious diseases physician and assistant professor at McMaster University in Hamilton."Parents who may not be encouraged to go get tested in their local communities will readily take their kids to the school, which is a place they know," he said."Things like this are going to be canaries in the coal mine. You kind of get a better sense of what's happening in the community by doing these local testing strategies."He added the caveat, however, that the type of test being used will likely cause more chaos for families and schools.For the pilot, Ontario is using PCR testing, which detects the genetic material of a virus. Although considered the gold standard, it's also so sensitive it would "pick up kids who are infectious, as well as kids who were infectious two, four, six weeks ago," Chagla said.He suggested that they could have chosen rapid antigen tests, which flag active infections by identifying proteins on the surface of infectious virus particles.The rapid antigen tests may offer a more precise picture "of who is really a threat to the community versus who had COVID six weeks ago, where they're not really a threat," Chagla said.WATCH | Nova Scotia offers rapid COVID-19 tests in Halifax for asymptomatic cases:Though Toronto parent Jessica Lyons welcomes the introduction of asymptomatic testing, she said it comes months late and should be offered more widely."This is desperately needed," said the mother of two school-aged children and an organizer with the Ontario Parent Action Network."Much more testing in schools — to make it accessible, to make it easy for parents and families and students to do — is really essential. So we support this pilot, obviously, but we think that it should have come ... weeks and weeks ago, and it needs to be expanded."Back in Thorncliffe Park, among the Toronto communities hardest hit by COVID-19 this year, parents in the neighbourhood expressed concern about the new positive cases found through the testing initiative. But they're also adamant about one thing: their schools staying open.Remote learning last spring was "really hard for kids. We've seen the mental stress on our child and other kids," said Osamah Aldhaby, father of a second grader who he said really missed being at school."When we were kids, you know, we used to run away from school," Aldhad noted."Now they're actually really wanting to go to school, which is really important for them."