Why do you think bad teachers would work their way out of the system due to competition? Ontario pays teachers generously and as a result has a glut of teachers (widespread unemployment amongst new teachers, people going abroad, certainly many of these people would be good teachers). There's no "competition" because the challenge is to get on the supply list, and then get hired into the unionized workplace. Once you're there, don't worry about getting fired. The main struggle is getting in, not avoiding getting out. High pay does necessarily lead to the sort of competition that I think you have in mind.