In order to teach in publicly funded primary or high schools in Ontario, you need to obtain your certification from the Ontario College of Teachers. To teach in publicly funded ESL programs for newcomers, you need a certification from Teachers of English as a Second Language Association of Ontario.
But don’t despair. There are still tons of teaching opportunities for internationally-trained teachers who have not yet obtained these certifications. Most private primary schools, high schools, language schools, and after-school centers do not require such certifications. However, please note that certifications, such as OCT and TESL Ontario, can still boost your chances of landing a job in private educational institutions.
This information is based on laws in Ontario on May 4, 2020.