Today, President Bush created a controversy when he said that schools should teach both evolution and intelligent design in science classes. He is wrong though, and appears not to understand exactly what science is.
Now, I want to preface this by saying that I believe that as a matter of fact, God DID design our universe, and create the earth and all things that are in it. Science is only investigating the mechanisms by which He did so. If you want to learn more about my Church, go to Church of Jesus Christ of Latter Day Saints.
However, that is my own belief, which is based on my faith (and faith is a belief in things which we do NOT see or have a perfect knowledge of). It may or may not be your belief. And even if it were everyone's belief (as the idea that the sun was some kind of a deity once was), it would still not qualify as science. Science does not deal with beliefs, it deals with observed data, and the conclusions that this data has led to by the use of the scientific method. If you can show me some specific, measurable, scientific evidence that God did what I believe (in fact, what I know) He did, then it belongs in a science class. But lacking this, it does not, any more than it belongs in a gym class (where people study physical education) or in a French class (where people study French). Of course, it is entirely possible that it may come up tangentially in a discussion in ANY of these classes (and I'm certainly not against saying the word, 'God' in a school if it comes up in such a freethinking discussion), but it should not be MANDATED by the President or by a local school board or by anyone else unless we can show that it is directly part of the subject taught. For that matter, theology is taught in a variety of churches, but no one would suggest mandating that every Sunday school class that discusses creation should include a description of Darwin's observations.
Now, after this point is made, the next step is that people who want to push non-science into a science class will invariably claim that evolution is 'an unproven theory' and so it is no more 'scientific' than intelligent design.
Conceded that evolution is an unproven theory. But then, so are most theories in science (for example, no one has formally proven the Theory of Gravity either-- we just know it works as described by Newton). There is more and more evidence all the time to support evolution (be it the discovery of fossils, genetic experiments, observation of natural selection, DNA linkage, etc.) while I have yet to see any purported evidence that it is false that holds up under closer scrutiny.
The best parallel to the scientific method in a non-science setting is the practice of law. A theory is put forward (i.e. that a person committed a crime). Evidence is collected to support or refute that theory. Ultimately a decision is made to either accept or not accept that theory (with the knowledge that we may have accepted a false theory, although hopefully not, and so hence there is an appeals process so that the theory undergoes continued scrutiny). A competing theory may be offered (i.e. that someone else committed the crime), but unless the defense can submit some hard evidence in its favor, it is not likely to be taken seriously by the jury.
In that framework, the Theory of Evolution was put forward based on the original observations of Darwin. Since then, it has been looked at critically for decades but has held up under all of the attempts to prove it false. Intelligent Design (which is not, incidentally, in contradiction with evolution) needs to be similarly supported by some kind of observable evidence before it meets the standard by which it can be taught in a science class.