Well, Darwins theory is to be taught the same as every other theory. The reason they won't teach Creation is simple. It's unconstitutional. I believe they passed this sometime in the 50's and teachers have been fired for trying ever since. I believe I have even met a few out of my 15 years in public education (please don't be as stupid as I was and pass your classes...)
Either way, most christians debate the theory not only because it goes against their religion, but they also think that it sounds rediculous. Well, if its so "un-provable", what happened in the Gallopagos Islands when they discovered all of those birds and turtles who had adapted to their environments? I'm just saying...that sounds a lot more probable than a book that a bunch of schitzofrenics wrote....