here in ottawa, most teachers receive part time contracts for each semester of class. full time positions are highly competitive, and being a part time teacher does not guarantee you'll be considered for a full time role. in ottawa (as i'm sure in all cities/provinces), there is a teacher's union and full time teachers get preference over any new job posting. this means if a job posting comes up, the school will exhaust all current full time teacher applications before interviewing applicants who are currently part time or from outside the school. At the college i worked at (non-teaching role), part time teachers had no preference over the public when it came to open positions. perhaps this is school specific, though i'd guess all unions have similar rules.