Seven Toronto District School Board (TDSB) schools are among the 27 in the province who have reported COVID-19 cases.
All seven cases have been attributed to staff members, four at elementary schools and the three at high schools.
Earl Haig Secondary School, York Mills Collegiate, and School of Experiential Education are the secondary schools to confirm infections.
Earl Haig is one that was identified by the TDSB as having a potential classroom shortfall as 78 per cent of the student body or 1423 students will be returning when classes start on Thursday.
Brookhaven Public School, Bloordale Middle School, Don Mills Middle School and Charles G. Fraser Junior Public School also all reported cases on Tuesday.
Elementary schools began a staggered start to the school year on Tuesday with the return to class happening over three days.