Much is being made of the latest law in Tennessee aimed at opening space in science classrooms in that state for "alternative theories" on evolution and global warming. The fact that organized forces behind these two issues - which otherwise have nothing to do with each other - have joined together in this case tells us what we already know: that this is about politics, not science.
In point of fact, it's always about politics first. That is the nature of things. Because we have, at root, two fundamental systems in play here. The first is the system of science, which at its heart is not about this theory or that but about a basic set of rules - evidence, hypothesis testing, replicability, peer review. Evolutionary biology is the result of the scientific method. In this sense, a law which allows teachers to consider alternative evidence and hypotheses is, on its face, not anti-scientific - which, I'm sure, is why it was written that way.
The problem comes in the context of school classrooms, because schoolchildren are at an inherent disadvantage. There is no peer review in school, because the teacher is an authority figure and the students in little position to argue. Classrooms, especially in elementary and middle schools (but to a substantial degree in high schools as well) are not about doing science (following the scientific method), but about teaching the results of science - that is, what other scientists using the scientific method have found. This is what "state standards" are about, because standardized tests do not (and cannot) get at whether a child has learned to think like a scientist - only whether he or she has learned a body of material already gathered by other scientists using that method.
So this latest round of the debate in Tennessee is really about muddying the issue. By trying to pretend that sixth or eighth graders are scientists (not consumers of the results of science), folks with particular agendas (political, theological, or otherwise) hope to use the confusion to win what they cannot otherwise.
And this is where the system of science (the development of knowledge) and science education (the transmission of that knowledge) run headlong into another system: democracy. Our system of public education is founded on democracy - indeed, as Mark Twain put it, "public education is democracy".
But that has meant, historically, giving the local community substantial control over the curriculum. The alternative - to put control over the curriculum into national hands - is to centralize power, the results of which depend very much on who wields that power. It is anti-democratic, and contrary to the founding principles of the Constitution.
So we praise the democratic system that allows local communities substantial control over what their children are taught. But what then if the majority of some local community wish their children to be taught strict creationism, or that the world is flat, or the political dogma of this or that political party? If the community as a whole feels strongly enough about it, that is what will be. Will the children in question suffer? That depends very much on your point of view - for some, ideological purity will seem more important that openness of mind and an ability to move from the reception of scientific knowledge to the creation of new knowledge.
Historically, democracy itself has provided the mechanism for balance. A few years ago, proponents of creationism briefly won control of the Kansas Board of Education - only to get swept out of office in subsequent elections. The same happened in Dover, PA, after a highly-publicized court case. It seems that, when push comes to shove at the ballot box, a majority of Americans even in otherwise-conservative areas prefer to let science run its course than to overrule it with ideology. So it may well be in Tennessee. And if not - if Tennessee becomes the anti-science state - there are 49 other states that will be more than happy to take up the slack.