14 billion, not 6,000
One side says: weird, weird, weird. How can it be forbidden to go on from (1) to (2), (3), and (4)?
(1) The universe is 14 billion years old.
(2) The bible says it's 6,000 years old.
(3) If it's 14 billion years old, then it's not 6,000 years old.
So, (4) The bible is wrong about the age of the universe
All the fun started with Michael DeDora here (you can find out what the initial issue was there) and the insults started with PZ Myers here, then there was this from Massimo Pigliucci, and this from Jerry Coyne, and then this from Ophelia.
Here's the other side. First, therere's the problem that saying (2), (3), and (4) picks on one religion. Hindus and Buddhist believe in a universe with an infinite history (or so I recall). How can it be right to spend time attacking biblical ideas, but ignore Hindu and Buddhist rivals? That doesn't sound very even-handed.
Second, there's a problem with (3). Different religions have different ideas about religious truth. Scientific truth is one thing, "sacred truth" is another, some say. So the earth is 14 billion years old, but it's also (in some sense) 6,000 years old. So some reject (3). Now, that may be poppycock, but could it really be a science teacher's job to get into it? What training do public school science teachers have in these philosophical matters?
Third, there's a question of the deal we've struck on these issues. Many fundamenentalists really don't like having (1) taught in school, because they think (2) and (3) are true, and they don't like the implication that (4) is true. As I understand it, the deal we've got now is--science teachers get to say (1), if they don't say (2), (3), and (4). Now, to many religious parents, they're already getting the raw end of the deal. They know their kids are going to be thinking (2), (3), and (4), even if only (1) is openly stated. So the deal is fragile and fraught, and there are frequent battles about it. In that context, is it really wise to ask for more?
Fourth, as a parent, I'm rather sensitive to what's crammed down my kids' throats during school time. I think I'm entitled to be the primary shaper of their attitudes on religious and moral matters. Occasionally teachers stray into these private, family areas, and I don't think "Oh wonderful, my kids are being asked to critically scrutinize their beliefs." Not at all, because lower level education is rarely about crticial thinking. The teacher is right (actually, more often wrong when they get into religious and moral matters), and that's that. What I think is "butt out." To be consistent, I must take the side of religious parents who would want a science teacher to butt out and say no more than (1).