I am allowed to teach anything in my state as long as I am certified to teach one thing. So if I am certified to teach English, the school can still (and did) put me as a teacher of a Math class. It doens't matter if I haven't taken that math class since 8th grade. I also didn't plan to chaperone dozens of hormones ravaged teens on the Texas coast with just a bus driver as the other adult (while being held responsible for their actions), because I got ""assigned" to be Senior Class Advisor.
I have no idea what servicemen actually sign when they sign up, but I figure there is some little clause in there to cover such situation. But the point is we all get sold a bill of goods when we get jobs, and we deal with them until the contract runs out.
I will say that I find the fact that people are NOT being let go when their contracts are up something totally reprehensible but once you sign a contract that has a loophole and you should know it if your read it, you are committed in my book. No matter what the sales pitch was.