You'll remember that the Dover, Pennsylvania School District has decided to include intelligent design in its curriculum. As this story notes, there's some pretty heated complaints in the neighborhood as a result. This story says the Pennsylvania ACLU is looking at the case, but hasn't yet decided what to do. (My own calls to them on the subject were not returned.)
Meanwhile, this editorial by Nancy Snyder seems to argue in defense of science, making the point that the schools should also teach the weakness of intelligent design.
But in the end, this editorial still makes the "equal time" argument, saying that
If a political science teacher presents the problems of the Democratic and Republican parties and makes students aware of the Libertarian party, without critiquing that party's strengths and weaknesses, that teacher has overstepped constitutional bounds. . .. Public school science curriculum that assesses the weaknesses of Darwinism must also assess the weaknesses of competing theories.
It's a fair point that the ID proponents are really trying to proselytize, not to teach. But the Democrat/Republican analogy is deeply misleading. Evolution is not like a political policy dispute, where there are pluses or minuses to taking one view or another. Reasonable people can disagree over the desirability, of, say, an earned-income tax credit versus a minimum wage increase. But there is no similar dispute over the scientific validity of evolution. Teaching "alternative theories" of the origin of species to ensure fairness is just as valid as teaching children that the earth might be flat or it might be round--or teaching them that the earth might orbit the sun, or the sun might orbit the earth--out of "fairness" to flat-earthers and geocentrists. Ms. Snyder concludes that "Discussing the unanswered questions posed by Darwinism and intelligent design and researching studies that explore those unanswered questions is effective science instruction." But it is just as effective as teaching students the unanswered questions raised by astrology and the users of divining rods.
But aside from the alleged "effective[ness]" of such education, Ms. Snyder argues that it would be legal to do this under the First Amendment. That is not necessarily the case. It is true that the Supreme Court said in Edwards v. Aguillard, 482 U.S. 578, 594 (1987) that "teaching a variety of scientific theories about the origins of humankind to schoolchildren might be validly done with the clear secular intent of enhancing the effectiveness of science instruction," but the point is that intelligent design is not a scientific theory--it's a religious statement, and that makes all the difference. The First Amendment doesn't prohibit schools from teaching bad science--in fact, the First Amendment does not prohibit schools from teaching students that the earth is flat, or that divining rods work. But it does prohibit the government from propagating a religious viewpoint. Intelligent design is a religious viewpoint. Thus Ms. Snyder's suggestion that "teaching the flaws" in intelligent design would render it a legitimate subject of instruction in a government school is incorrect.
Suppose a Catholic parent insists that the school district teach students that transubstantiation is literally true. A Protestant parent then steps up and says, "No, we ought to teach students that transubstantiation is just metaphorical." The second view may be more "moderate" in some sense--but it is hardly more legitimate a subject of instruction in a government school. In the same way, teaching students the flaws in intelligent design might moderate the fury of those parents who care about the scientific literacy of their children, but it would not render teaching religion constitutional.
The distinction here might seem like a subtle one. Government employees may teach students that some people believe in transubstantiation. They may teach students that they must respect people who believe in transubstantiation. They may assign Catholic students to give the class a presentation about what transubstantiation means. They may sponsor student debates in which a Catholic and a Protestant student debate the theological validity of the concept. They may invite students to write essays or poems about how they feel about the subject. A teacher may even tell students "I personally am Catholic, and I believe in transubstantiation." But a teacher may never say "transubstantiation is true," or "transubstantiation is a valid scientific concept, and here is the evidence for it." The state may not endorse a religious viewpoint. The same is true of intelligent design. The one thing that a government school may never do is say "intelligent design is true," or "intelligent design is a valid scientific concept," even if the teacher then goes on to explain various shortcomings in ID. Teachers may use ID as an example of a poor scientific theory, or as an idea of a contemporary mythology. Teachers may invite students to discuss their own personal views on the subject. But teaching it as a valid alternative to evolution, that just happens to have some flaws, is bad science education, and is unconstitutional.
In McLean v. Arkansas Bd. of Ed., 529 F.Supp. 1255 (D.C. Ark. 1982), the law did not prohibit teachers from teaching the flaws in creationism. Nevertheless, the court struck down the law requiring creationism education because
The State failed to produce any evidence which would warrant an inference or conclusion that at any point in the process anyone considered the legitimate educational value of the Act. It was simply and purely an effort to introduce the Biblical version of creation into the public school curricula. The only inference which can be drawn from these circumstances is that the Act was passed with the specific purpose by the General Assembly of advancing religion. The Act therefore fails the first prong of the three-pronged test, that of secular legislative purpose, as articulated in Lemon v. Kurtzman. . ..
Id. at 1264. So I don't think that "teaching the flaws" in ID would make it a proper subject of discussion in a science class--or a legal one.