Allowing faith in science class sets precedent for kids to supplant mysticism and superstition for rational thought and evidence, two vital ingredients in the solid foundation of all scientific disciplines. Science teachers do not just fill in blanks with whatever religion conveniently gives explanations based on assumptions and a complete absence of research. What happens when two religions give equally logical explanations of the same event? What makes us choose one over the other? Faith? What if subscribers to various faiths were in a science classroom and being taught Christian Creation? That is not "teaching". It is indoctrination and it transforms the classroom into a mission.
The argument is caused by fundamentalist Christians' assertions that the theory of biological evolution is false because the Bible already has a story for the creation of humans (as we currently are), and the theory of evolution is incompatible with it. Well, evolution happens. It's true and it's been proven again and again. It's the Fundamentalists' responsibility to reconcile their beliefs with the truth, not the other way around.
In America, science and Christianity are estranged. In 2005, fifty-one percent (51%) of Americans did not believe in Evolution. These people believe that God created humans in their current form, as written in Genesis, and they want to teach not only their own children this, but ours, yours, his, hers, and everyone else's kids. Bill O'Reilly gave pretty much the worst reason ever for wanting schools to teach the Christian version of creation. He said that Christianity had answers that science couldn't provide, such as how the world began. Apparently, it doesn't matter how one arrives at the answers, just as long as the teacher has answers handy. Following that logic, we could allow teachers to make things up, as long as they have answers to questions. If science can't provide the answers then why would we bring something that is not science into science class? If science doesn't have the answers to a question, that is exactly what the science teacher should say. If the student wants answers that science cannot provide, then the student needs to search elsewhere. It belongs in a class where unproven speculations are welcomed...whatever class that might be.
In Europe, there's really no debate about evolution. Nearly everyone accepts the truth of evolution, including Christians. In one of the most poetic statements committed to words, Cardinal Ratzinger says the following in his commentary on Genesis:
"We cannot say: creation or evolution, inasmuch as these two things respond to two different realities. The story of the dust of the earth and the breath of God, which we just heard, does not in fact explain how human persons come to be but rather what they are. It explains their inmost origin and casts light on the project that they are. And, vice versa, the theory of evolution seeks to understand and describe biological developments. But in so doing it cannot explain where the 'project' of human persons comes from, nor their inner origin, nor their particular nature. To that extent we are faced here with two complementary -- rather than mutually exclusive -- realities."
Because Genesis is a Jewish text, I also consulted Jewish opinion on the matter. According to the Rabbinical Council of America, "Evolutionary theory, properly understood, is not incompatible with belief in a Divine Creator or with the first 2 chapters of Genesis." So, really, why is there even a debate? Science teachers are teaching the SCIENCE behind whatever the "Divine Creator" may have created. They are not telling children not to believe in God. That doesn't belong in science class either.
Some Christians issue arguments from more solid ground and only claim that we should teach Intelligent Design in science classes. I don't really have anything against Intelligent Design. It can be defended just as easily as non-design, in my opinion. I can very effectively refute any argument that claims "Intelligent Design is false". God/Divine Creator has the most powerful trump cards imaginable: he is omniscient and omnipotent. With those two attributes, literally nothing is impossible, so defending him as the creator of the universe is not challenging. But, virtually all supporting evidence for Intelligent Design has been thoroughly researched and the results invariably suggests logical explanations concurrent with scientific theories. This, by no means, invalidates the concept of Intelligent Design, it just makes the reasons for teaching it superfluous. A grand designer may have set evolution into motion, but in order to debate the existence of a designer, no matter what stance is argued, we would have to speculate with no way of verifying our speculations. If a student asks if Intelligent Design is true, the correct answer is "maybe" or "I don't know." There's nothing else to say about it.