I think you've got an interesting idea going here. If creationists use the "balance" argument to get creationism into schools, their unwillingness to teach science (not to mention other religious and philosophical ideas) in church kind of constitutes a double standard.
Problems come in when you consider that the ID movement is working hard to make people believe that they are a legitimate science that is not strictly tied to Christian theology.
Also, like Moose said earlier, you have to consider that schools are public institutions, whereas churches are in the private sector. Each system has its way of allowing the individual members to decide what goes on. If you want something different taught in schools, you have to petition and/or vote accordingly, etc. Religion has a way of letting you choose what you are taught, too: you go to a different church somewhere.
Religion has always enjoyed all sorts of immunities, at least in the USA. They are in the unique position of being shielded from attacks from anywhere while also being allowed to meddle in anybody else's affairs by simply claiming that it's part of their belief system. They are permitted, by law, to attack science, but science is not given entirely the same privilege to fight back, except in blogs and seminars. For instance, if a scientist wished to protest the activity of a certain religion in his hometown, he would not even be allowed a hearing in the local court. But, religion protesting the presence of science in its hometown can make it all the way to the Supreme Court of the United States.
It's unfair. But, really, if you think about it, that's the way science is: the scientific method allows anybody to challenge anything at anytime, and that's why science is so strong. Ironically, the protection that religion has gotten under the US Constitution is the reason why it will never have the strength of science, because it will never have to overcome the challenges to its central axioms that science experiences every year.
My apologies: I was under the impression that you wanted explanations for the current situation.
So I'm guess you would like to see the two ID / creationism and science left separate?
I am for science (and only science) to be taught in science classes. And I am also for the freedom of religion, which requires that no particular religious idea be supported in public institutions.
Here's my particular view on this. I am a Mormon, and many of my fundamental beliefs about the nature of God and the history of creation, etc., are vastly different from what other Christians believe. If they were to teach creationism in school, Protestant and Catholic parents would be happy, but my religious beliefs would be discriminated against, and Mormons don't have the numbers to get a popular vote passed.
And, in addition, there's just no scientific evidence for creationism, so it shouldn't be taught in science class.
But, if I were in authority to choose, I would want to teach at least basic science concepts in church. I think it is inexcusable to allow the ranting about science that I hear in church, but to not allow anybody who feels differently to challenge the views that are put forth. I have tried to rebut an argument in church, and I can testify that it's not good for your health or for your continued fellowship in the congregation to do so. "Church is not a forum for debate," they like to say, which is unfortunate, because there is no way provided for people to discern which parts of what is said are true and which parts are not.