What about the opposite situation? Suppose the teacher told the class there is a God?
If that's all she said, then I doubt anything would happen in either state. Simply saying that God exists is really a minor thing. In fact, I'm sure I heard my teachers say on a regular basis things like, "Just hope to god that. . . " or something else like that. No biggie.
If she was trying to indoctrinate the children to the point that it made some of them uncomfortable enough to tell an adult, then she'd most likely be punished/lose her job. Definitely in California, possible even in a place like Alabama as well.