I teach both math (algebra & geometry) and biology and am certified for both. I teach at a private, struggling boys Christian high school in lower manhattan. I've entertained thoughts of trying to move to a place such as a charter school but having heard that my transition could put my career at risk makes it very unlikely that I'd ever pursue the change. Even if the salary is significantly greater, why change and risk not having a job the following year. This system really hurts itself. Many long term, excellent teachers wouldn't mind a change, but not if tenure is lost and jobs are always at risk. I would love to teach and impact public school students but it is a frightening concept. (I've been in Who's Who of American HS teachers more than once...but this would mean nothing in terms of going to a new school and being retained.).