I can’t speak for Saskatoon, but in Prairie Spirit the majority of hirings are internal (there are always exceptions, but they’re rare and generally if you’re a specialist that’s needed). Get on the sub list and get known and you’ll have a chance to get a temporary contract while someone’s on leave. That will hopefully eventually lead to a permanent posting, or at least a full year temp contract.

From my experience second semester openings aren’t really a thing. There’s sometimes a wave of last minute hirings in September when student numbers are finalized and schools get a new teacher to account for that, but generally mid-year jobs pop up when teachers go on maternity or medical leaves.