The Toronto District School Board has created a page providing a list of the active confirmed cases of COVID-19 among students and/or staff in TDSB schools. 

TDSB: COVID-19-Advisories

The Ontario Government has also created a site that reports a summary of COVID-19 activity in publicly-funded Ontario schools. Data is published on a daily basis during the school week.

Ontario: COVID-19 cases in schools and child care centres