Ontario's slowly rising COVID-19 caseload concerns Education Minister Stephen Lecce as students in much of the GTA return to school for the first time in six months on Tuesday.

As students in Peel, Halton, Durham and much of York Region return to in-person or online class instruction on Tuesday, Education Minister Stephen Lecce said he fears the rise in daily infections across Ontario, which have stayed above 100 for the last 11 days, could impact continued operation of schools.

"The singular concern I am noting is that increasing number of cases in our community," Lecce told CP24, adding that everyone needs to "redouble" their efforts on physical distancing and hand hygiene.

"In the context of flu season and a possible second wave, we cannot lose focus," he said.

Case growth has been highest in Toronto and Peel Region, sometimes accounting for half of the province's new infections on a daily basis.

On Tuesday, provincial officials revealed that labs confirmed 375 new COVID-19 infections over the past 48 hours, including 190 on Sunday and 185 on Monday, the highest count of cases since July 24.

University Health Network Epidemiologist Dr. Issac Bogoch said there is no way to keep infection growth in the community from impacting schools.

"The rate of introduction of COVID-19 into schools will be completely reflective of how much covid-19 there is in the community," he told CP24.

Lecce said that public health officials have not provided any sort of maximum number of cases required before they recommend that schools be shut down once more, saying instead there are a number of indicators they would look to.

"There's a few variables public health officials and the (Chief Medical Officer of Health) would consider in that respect," Lecce said.

Ontario's roughly $371 million plan calls for high school students to attend truncated classes on alternating days, with masks mandatory for all students down to grade 4.

It also embeds public health nurses in the school system and provides all students with the option to learn from home.

Lecce and Premier Doug Ford were forced to expand funding for the plan and allow school boards to spend up to $500 million contained in their reserve funds amid continuing criticism that the plan does not provide for adequate physical distancing in elementary school classrooms.

The federal government later announced $381 million in additional funding to help.

NDP education critic Marit Stiles said the rise in cases should give the Ford government pause about the plan.

"COVID-19 infections are on the rise again in Ontario, and most children are being sent into a school and a classroom where they can’t possibly physically distance. Yet the legitimate concerns of parents, teachers, education workers and kids are being brushed off by Education Minister Stephen Lecce and Premier Doug Ford," Stiles said Tuesday.

"Students and staff don’t need to hear a defence of the Ford scheme. They need to see action to divide up classes into smaller groups."

Bogoch said there is no more time to make changes to school reopening plans, and officials need to focus not on individual cases detected in schools, such as the five detected in Ottawa schools so far, but whether transmission is occurring within the school setting.

"Our time is up – it's go time, kids are going back, there is no time to start reijigging these protocols and plans. I wish I could say more than hopefully, but that's the actual word now, hopefully, that we don’t see transmission within the school setting."

Asked about distancing of only about a metre between desks in one Grade 8 teacher's classroom on Tuesday, Lecce said distancing was always just one of many measures needed to prevent the spread of infection in schools.

"You have to have a bundle of efforts, a package; (physical) distancing coupled with the fact that Ontario is masking every student, combined with enhanced cleaning, screening of every child and a very robust testing program in the province, together all of that – in addition to the changes in our schools – staggering starts – we're doing everything possible."

Epidemiologists directed by Sick Kids Hospital called one metre of distancing between desks the bare minimum they could recommend.

Lecce acknowledged that some school boards, including the Toronto District School Board, are targeting their "package" of efforts at schools in areas previously connected to high rates of infection.

He stressed that community transmission of the virus, left unchecked, could defeat every plan put in place and force his government to close schools once again.

"What will happen in our schools is reflective to what will happen in our communities."