David Velleman has a nice, balanced post up about ID and schools. I don't quite agree with everything, but he's close to being right on everything. My first comment makes my views clear enough, as if my post here didn't already do so. There is a little more in that comment than I said in the post, though, and this is more succinct, so I'm reproducing that comment here for posterity along with a second comment clarifying some elements of evolutionary theory that are philosophical arguments:
David, you are one of the few non-supporters of ID who will actually admit to what ID supporters want and not pretend it's something else entirely. Most of them would be pretty happy if biology teachers presented the ID arguments and then presented arguments against them.
My post wasn't accurately portrayed, so I want to supplement Mark's description of it. I do think ID arguments are philosophy. Those who claim they are science are strictly speaking not telling the truth, but I think they can be excused, because all sorts of philosophical arguments show up in scientific reasoning. Any view in theoretical physics involves some metaphysical assumptions. Evolutionary theory usually involves philosophical reasoning. So I don't have trouble calling ID science if science includes those things.
On the other hand, those who say ID is pure religion should not be excused. The latest person to disprove that claim is the now-deistic Antony Flew, who accepts the ID arguments but is about as unreligious as you can get. He absolutely detests most religions. He isn't the first, however. Michael Denton is an atheist, and he's critiqued evolutionary theory with arguments that would fall under ID. He's agnostic on the actual mechanism, but he thinks the ID people are onto something. He's just not sure what. He doesn't think it's God.
You don't need to turn to non-religious people to show this, though. All you need to do is look at what ID proponents are saying. The ID arguments are not religious. They're simply teleological arguments, which have always fallen under the category of philosophy. The conclusion is not that the God of the Bible is real and that the Bible is true. It's not that Christianity is right. It's not that the designer didn't work through evolution. It's not even that the designer is good. It's that design has occurred at some point and somehow. In the physics ID arguments, the designer has to be responsible for the creation of the universe (or at least for the cosmological constants' having the values they have). In the biological ones that ID opponents like to pretend are the only ID arguments, the conclusion is simply that if evolution occurred it was helped out by some designed process. That's consistent with evolution not having occurred, and it's consistent with some designed process speeding it along. It's consistent with miracles that violate the laws of nature, and it's consistent with a deterministic process that the designer set into motion that in microscopic view might look like random chance. The conclusion is thus far from any religious view. It's some set of conditionals or disjunctions, however you might express them, and the options involve ones consistent with the most popular religions but also some that are consistent with the falsity of all religions. One possible conclusion is even the view that aliens helped our evolution along, though hardly anyone who seriously knows these issues opts for that as their favored view.
The only arguments I've ever seen that claim that this is not philosophy are not really arguments that ID isn't philosophy. They're arguments that it's bad philosophy in the same way that a materialist will argue that dualism is bad philosophy. That doesn't mean it's not philosophy anymore than the failure of Descartes' arguments could mean that he wasn't doing philosophy. It also wouldn't mean it's not science under the extended account of what counts as science that includes the kind of philosophical reasoning involved in evolutionary theory. At best it would mean it's bad science, as racial essentialist biology was a hundred years ago. Bad science isn't not science, in the way biblical interpretation is not science, and bad philosophy isn't not philosophy in the way that sociology is not philosophy.
Here is the second comment in response to a query for what elements of evolutionary theory are philosophical arguments:
As you acknowledge, empiricism and naturalism are philosophical theses, and the motivation for evolution originally came from the desire to have a naturalistic theory of the origins of the human species. That was a philosophical motivation. Empiricism is an epistemological thesis (a controversial one that many philosophers recognize as self-undermining, I might add, because you can't observe that empiricism is true with your senses, but it claims that you shouldn't accept something without knowledge through your senses). The justification for pushing off explanations that don't involve entities we can observe with our senses or entities whose causal effects we can observe with out senses is thus based on a philosophical argument. Therefore the reason people are so opposed to ID is not a scientific one except in the extended sense that philosophical arguments like ID can be part of scientific reasoning. The very argument against ID is self-undermining.
One philosophical issue in any field of science is what counts as a good explanation. That's especially important in evolutionary theory, because you're trying to observe something you can't see and can't reproduce. It's not proposing a hypothesis of some general principle and then testing to see whether it's true. That's science. It's science that relies on philosophy, though, because our discovery that such methods are good methods is essentially an epistemological question. Hume's challenge to scientific laws (or at least our knowledge of them) must be overcome if we can have scientific knowledge at all. So the elements of evolutionary theory that the biological ID people like the Discovery Institute will accept are science but in ways that require philosophical argument, just as is the case for any scientific reasoning.
Now when you come to the parts they question, you're certainly getting into less secure science. You're trying to propose a theory that explains what happened millions of years ago. You're not simply proposing something that we can now test. You can do that, but all you get is what all the Discovery Institute admit to, things like development within a species over time through natural selection and random chance. You don't get what some of them deny or aren't sure of, things like common ancestry of humans and all other species. That's a historical thesis, not an immediately empirically testable one, and thus it involves more philosophical argumentation than other scientific theses. It's thus more like the Big Bang. Stephen Hawking's books basically deal with more sophisticated versions of classic philosophical arguments like the cosmological argument and the cosmological constant teleological argument (what I've been calling the physics ID argument). That's philosophy just as much as it's philosophy to interpret the equations of quantum behavior in terms of wave form collapses and the metaphysical status of the existence of cats. You can argue that it's still science, as this philosophically informed discussion does, but that's an argument that requires certain philosophical moves, and so it's not the kind of science that disallows things like ID arguments as being science on the ground that they're philosophical arguments, because philosophical arguments are part of science in the evolutionary argument.
Another key philosophical question that comes up in evolutionary theory is speciation, which assumes a theory of what it is to be a species. That's a question in the philosophy of biology. See the Stanford Encyclopedia of Philosophy entry on it for more. Also, since the origin of life is at issue, what counts as life is relevant, and that's a metaphysical question as well, one hotly debate in philosophy of biology. See the Stanford Encyclopedia entry on that. Teleological notions also play a role in evolution, both historically with vitalism and its rejection and more recently with the shorthand kind of talk that treats evolution as having a goal. Both issues have to do with teleology and at least partly come under philosophy. Again, see the Stanford Encyclopedia entry on that for more. Michael Ruse claims that there are further philosophical theses in evolutionary theory that have actually caused the ID debate to surge.