How do principals deal with teachers who leave or die during the school year?

I'm a first-year teacher on an alternative certification program, and somehow I got myself thinking, teachers can p away unexpectedly during the school year....they could die in a car accident, older ones could have a heart attack or something, or they could commit suicide due to the high stress level. Or they could get arrested and go to jail (nobody's perfect!). So what happens then? Does the principal place a job ad since it's now a "teaching vacancy"? Does he hire a long-term sub? Even then, it'd be hard for the new teacher to keep the "old" clroom going, since no two teachers are exactly the same in terms of teaching style and clroom management. Don't worry, I'm not thinking of dying yet, but still, I have this one rowdy/disrespectful cl that COULD (I'm not saying they will necessarily) drive me over the edge and cause me to off myself. I'm sorry, it seems I can't post a question on Y!A without mentioning suicide....I guess I've got issues. But still, it's always possible for teachers to die unexpectedly. People die, that's part of life.