Teach Science Early
This just goes to show you that we need to start teaching critical thinking skills as early as possible. I don't think the beginnings of critical thinking are beyond the average late-elementary school kids, say eight to ten years old.
Of course, those fundies I used to hang around with never really supported me when I tried to get their ten-year-old to think critically. Now, I see why. I wonder if it was intentional on their part?