Below is an interesting video which suggests that children as old as 6 are subject to a subtle form of indoctrination during English lessons:
First graders are taught how to use emotionally manipulative language to advocate for "social justice", and "to use their voices to advocate solutions to social problems" (Is it even something which children of six should be thinking about?)
The textbook featured in the video learns children how to use "emotional words" with such nice examples as "My Mom always nags me to clean my room." (Sounds downright disrespectful to me.)
Or how about this example of finding solutions to social problems?
Students are taught how to create the feelings of anger and fear in their readers to solve the problem of the lack of books in the library:
"The major got a raise, but the kids do not have books!"
While I wouldn't go so far as to call it indoctrination, it's still manipulative and I understand why parents are concerned. This does make homeschooling sound like a good option, doesn't it?