I don't know if this will be allowed but you might suggest that the school look at the lesson plans that your son's teacher submitted for approval. (Lesson plans must be submitted in writting in advance of instruction.) They may be good ammunition for you. BTW those lesson plans if recorded as he was teaching the course also put the principal of the school in hot water because the plans are suppose to be reviewed by him.
I made my case and they immediately agreed with what I had to say. The Principal pulled out his copy and showed a couple of stickies he'd put in the book himself.
We displayed the textbooks we had borrowed from the curriculum director that were the ones that the teacher was supposed to be using.
We were told that the point was moot. That the teacher was going to use the correct textbooks.
Something didn't feel right, so I pressed the issue. I asked if the book was going to be removed immediately and an actual science book be used in its place. I got a defense about the teacher using several science books to teach the class and that the correct textbooks would be one of them. I was told that teachers are entitled to their beliefs. I was told that maybe, possibly (baloney) the teacher was using this stack of pseudo-science textbooks to teach the children to think critically. They had no proof of this, but they presented that defense anyway. They hadn't even talked to the teacher about it.
I firmly shot down each and every argument. I got them to agree that the crappy textbook would be removed from the 8th grade next week and the new textbooks would be used instead.
Then I asked about the 9th and 10th grades which were also using that fake "science" textbook. They said that this was the only textbook they have for those grades and that they don't have money to purchase any others. We talked about alternatives, but there were few. We pressed the issue that they need a better curriculum approval process (this one slipped through, they said, but they're still going to allows its continued use in some grades).
We looked at the textbooks and saw that they were only used 1 year at the previous school that owned it. We confirmed that it was the previous school that had the most offense content excised from the book. We said that should be a clue to the school that they got bad textbooks.
The principal and director said that they would like to use the textbooks and my writeup about them as an exercise in critical thinking for the higher grades. I said that was an excellent idea, as long as they stop calling them "science" books when they're not science books.
Beyond pulling them out of the 8th grade next week, they wouldn't commit to anything. I will keep pressuring them and helping them find alternatives to the textbook as nobody should ever have to be subjected to the garbage that is in the books.
So, we won a limited victory and at least our daughter's class will no longer be using the books.