Parents: Why is there opposition to Creationism being taught in schools (even as an elective)?

There are thousands of religions in the world. Schools cannot teach them all. Christians would be rightfully upset if their tax dollars were used to teach paganism -- or even Mormonism. There is no official religion in the U.S. There is nothing to teach about creationism, it is only the bible and even Christians will disagree about the literalness and meanings that are intended in the bible. There are places that society teaches the young generations about science -- schools. There are also places that some families choose to educate their children in their faith -- churches. This has nothing to do with the President who was elected to put forth his ideas. That's his job.