I have a hard time sharing this as I find myself still trying to be politically correct but here goes: 
 I taught in the bush for 6 years. The main reason teachers leave is administration. They will give another reason, but their fellow teachers know differently. The admin are people who are good at talking and walking the line when needed and then turning around nod treating their staff in varying degrees of awfulness. I encountered this in 5 out of 6 admin (principals and vice). Until that is acknowledged and dealt with, teachers -many great - will continue to leave. Also, realize that those 'exit surveys' are not going to say "I'm leaving because my boss is a manipulative sociopath." I would have stayed in a town with no plumbing, continual sickness, and rampant substance abuse if all I had to worry about were the kids. Unfortunately for the kids, it's impossible to fight all fronts with and survive. Until the admin issue can be taken care of, there's not going to be a change.