BBC has a story about misfeatures in Indian textbooks, some of which are simple misspellings and some are--well, did you know Japan launched a nuclear strike against the USA during WW-II? I know they wanted to, and didn't know how to make a bomb yet, but ...
OK, the USA has a more consistent market for textbooks, they'll be better, right? Feynman found otherwise:
Finally I come to a book that says, "Mathematics is used in science in many ways. We will give you an example from astronomy, which is the science of stars." I turn the page, and it says, "Red stars have a temperature of four thousand degrees, yellow stars have a temperature of five thousand degrees . . ." -- so far, so good. It continues: "Green stars have a temperature of seven thousand degrees, blue stars have a temperature of ten thousand degrees, and violet stars have a temperature of . . . (some big number)." There are no green or violet stars, but the figures for the others are roughly correct. It's vaguely right -- but already, trouble! That's the way everything was: Everything was written by somebody who didn't know what the hell he was talking about, so it was a little bit wrong, always! And how we are going to teach well by using books written by people who don't quite understand what they're talking about, I cannot understand. I don't know why, but the books are lousy; UNIVERSALLY LOUSY!
Anyway, I'm happy with this book, because it's the first example of applying arithmetic to science. I'm a bit unhappy when I read about the stars' temperatures, but I'm not very unhappy because it's more or less right -- it's just an example of error. Then comes the list of problems. It says, "John and his father go out to look at the stars. John sees two blue stars and a red star. His father sees a green star, a violet star, and two yellow stars. What is the total temperature of the stars seen by John and his father?" -- and I would explode in horror.
My wife would talk about the volcano downstairs. That's only an example: it was perpetually like that. Perpetual absurdity!
(The essay goes on to explain how a blank book got a positive review.)
The math books I dissected for the local middle school (without any response to my evaluation, I might add) weren't quite that bad, but there were quite a few misfeatures. Probably some errors, too, but I didn't work all the exercises. I noticed that the "author list" included a lot of names, but very few of them had any background in anything but education. No "domain knowledge"
The kids' high school books were by and large somewhat better, though I hear some schools teach history out of Zinn. (I get it that this was supposed to be a corrective book to the old 50's-60's baseline histories, but if that's to be the new baseline you desperately need a corrective to it.)
I am perfectly willing to believe that the Common Core textbooks will be crud. It is a tradition.