Ontario’s public schools collectively reported another 168 cases of COVID-19 on Wednesday, posting average case growth of 30 per cent per day over the past five days.

The province says there are now 476 active cases of COVID-19 among students and staff across 4,844 of its schools.

The Ministry of Education says 390 of those cases are among students, 66 are among staff and 20 were in individuals not identified.

Over the past five days, the first five of the year in many regions, school-related COVID-19 cases have grown by an average of 30 per cent per day.

Toronto’s Chief Medical Officer of Health, Dr. Eileen de Villa, said Wednesday the growth of COVID-19 cases in the school system is her department’s biggest concern.

“Our biggest concern are the new cases of COVID-19 that are emerging steadily in schools. This is expected, given the transmissibility of Delta and the population of students under 12, who because of their age, can't yet be vaccinated,” she said.

The idea of whether schools are a significant source of transmission of COVID-19 is still under intense debate, and the early data this school year is made less reliable by the fact that the province’s guidance for testing is significantly narrower than it was last year.

Children without symptoms cannot access free testing unless they attend high school in one of 13 school boards, or have been identified as a high risk close contact of a confirmed case.

Provincial labs processed more than 33,000 test specimens on Tuesday, the highest daily total seen in three months, which may be in part due to testing requirements for symptomatic students to continue accessing schools.

The current school caseload made approximately eight per cent of all known cases in the province on Wednesday.

The school boards of the Greater Toronto and Hamilton Area are now reporting 167 confirmed or probable active cases of COVID-19, up from 109 yesterday and 50 on Sunday evening.

The Toronto District School Board is now reporting 33 active cases of COVID-19 across 27 schools.

The Peel District School Board reported 11 active cases of COVID-19, with nine classrooms or cohorts ordered to self-isolate.

And the Dufferin-Peel Catholic District School Board is reporting 20 confirmed or probable cases among staff and students.

Elsewhere in Ontario, an elementary school in Cornwall, Ont., which became the first in the province to close this school year due to COVID-19, reopened after a one-day closure due to an exposure.