Odds of Hanging On
Teachers and principals want subs they can trust. They want someone who can manage each class effectively and calmly, administer the work which the teacher assigned, and handle discipline in a consistent and measured manner.
If students are acting up, they want you to be able to deal with it. They don't want you knocking on Mr. Fustigan's door across the hall, and asking for help. Then you're just creating more work for Mr. Fustigan.
Engage the students, and don't just show movies. Yes, movies are fun for students, and sometimes even educational. But it'll be abundantly obvious to everyone at the school that you're doing the bare minimum amount of work. Somewhere, someone else in that sub pool will be willing to do a little more. Don't be the replacement who needs to be replaced.