>All certified teachers in Ontario may be assigned to teach math up to Grade 6

for grade 7 and over you need a qualification in math, however, you can still be assigned, so

>Therefore, even a teacher without a qualification in intermediate or Senior Division Mathematics can be asked to teach math in those divisions.

and

>The Respondent’s evidence is that due to the competitive nature of teaching positions, newly certified teachers may find that the only positions available to them are positions that require them to teach math, whether or not this was their intention. When few teaching positions are available, new teachers will often take positions outside of the subjects or divisions on their teaching certificate.

From page 3 (points 13 & 14) of https://www.otffeo.on.ca/en/wp-content/uploads/sites/2/2021/...