When it comes down to it, I don't believe we can truly know anything.
Also, people are using the original textbook excerpt to claim that these schools are teaching creationism as fact. Well... maybe the teachers are, but that entire quote was filled with "coulds" and "maybes" and "claims." It sounded a lot more like they were saying: "Don't blindly believe everything you read."
Which is kind of ironic, considering the source. Regardless, I think that principle applies to "science" and "religion" and is generally a good thing to teach kids.
In the context of evolutionary biology, even that sort of wishy-washiness is plenty damaging since, as far as we understand it, Darwinian evolution pretty much is a fact. Teaching kids not to blindly believe what they read is a laudable goal, but this is hardly the context to introduce it in, nor is it being introduced in good faith.
