Probably not as soon as you think. But if I were you I'd beat the Christian kids/teachers to the punch. Get a children's illustrated Bible and teach it as myth and explain that other mostly rational people think it's true, but they're crazy about this issue. My parents and in-laws are devout and sent such things as gifts. We used them, just not quite as intended. We have two well adjusted atheists in their teens.
If there is a god, I want to believe that there is a god. If there is not a god, I want to believe that there is no god.
