Teach them the (scientific) principle that we can judge the usefulness and accuracy of a theory by the predictions it makes, and how reality either behaves in accordance with those predictions or not. IOW, by experimentation we discover whether the theory should be retained or not.

Then start collecting examples of failed predictions (Darwin's ideas about the fossil "record", and infinite series of tiny changes between generations joining one species to another, just isn't there, for example) and successful predictions (God said Babylon would never again be inhabited, for example) ...

The math is quite simple and unavoidable on this basis.