The excellent and famous philosopher Thomas Nagel on teaching intelligent design:

When … in response to the finding that the teaching of creationism in public schools was unconstitutional, the producers of creation science tried to argue that young earth creationism was consistent with the geological and paleontological evidence, … their arguments were easily refuted. … That is a good enough reason not to teach it to schoolchildren. ..

I agree with Philip Kitcher that the response of evolutionists to creation science and intelligent design should not be to rule them out as "not science." He argues that the objection should rather be that they are bad science, or dead science: scientific claims that have been decisively refuted by the evidence. … However, the claim that ID is bad science or dead science may depend … on the assumption that divine intervention in the natural order is not a serious possibility. …

So far as I can see, the only way to make no assumptions of a religious nature would be to admit that the empirical evidence may suggest different conclusions depending on what religious belief one starts with, and that the evidence does not by itself settle which of those beliefs is correct, even though there are other religious beliefs, such as the literal truth of Genesis, that are easily refuted by the evidence. I do not see much hope that such an approach could be adopted, but it would combine intellectual responsibility with respect for the Establishment Clause. …

I think the true position of those who would exclude intelligent design … is that … the very idea of design is as dead as Ptolemaic astronomy … To exclude the possibility of divine intervention in the history of life is scientifically legitimate, and to assign it any antecedent positive probability at all is irrational. … Most evolutionary scientists … believe that there are no supernatural explanations, and that trying to show that they are incompatible with the evidence is a waste of time. … They think, Anybody who is willing even to consider supernatural explanations is living in the past.

We cannot, however, make this a fundamental principle of public education. I understand the attitude that ID is just the latest manifestation of the fundamentalist threat, and that you have to stand and fight them here or you will end up having to fight for the right to teach evolution at all. However, I believe that both intellectually and constitutionally the line does not have to be drawn at this point, and that a noncommittal discussion of some of the issues would be preferable.

I could see myself endorsing any of these standards for public school curricula:

• Democratic idealism – teach whatever the public wants taught, including some creationism

• Academic intellectual honesty – teach academia’s best honest assessment, as Nagel suggests above.

• Posterity futures – teach options to the degree betting markets say they’ll be accepted centuries later.

What I can’t endorse is the paternalism of teaching an elite academic norm that intelligence design, ghosts, UFOs, etc. are too silly to even consider, in order to correct a public biased to think these options excessively likely.

Added: See also Alex Tabarrok here and here.