We should teach evolution to our kids because:
1) It is the basis of all modern biology;
2) It provides the best explanation of how living things came to exist in their present form;
3)It fits the observations of thousands of scientists working over hundreds of years (Darwin used earlier discoveries to formulate his theory);
4) It makes predictions which have been verified (for example, that transitional -- "missing link" -- fossils will be found between one species and another);
5) Like the laws of physics and facts about the Earth's place in the Solar System, it is somewhat counterintuitive -- meaning it is not something kids will necessarily figure out on their own from direct observation;
6) After a certain age it is difficult to correct inaccurate ideas about the world. (Go to the article Unlearning Bad Science by John Merrow to read about the study which asked graduating Harvard seniors why it's warmer in summer. Nearly all said it's because the Earth is closer to the sun!)
7) We want our children to have accurate information about how the world works, so that they can make good decisions about how to run it when it's their turn.