Question: How do they make educational books?

I'm not sure if my question fits this subreddit, but I've chosen to post here because I can't find the answer by googling, and the people here might have knowledge of the subject.

My questions is, how do the people who make educational books - and by that I mean official books used in schools, actually make them? How do they know what to put in the book? Which sources do they use? Where do they find the information they put inside, which I can't seem to find anywhere else on the internet? (For example, certain details and conclusions of some literary work.) In general, what is the process behind making those books?

The main reason why I ask this is the sources. School books often have very useful information that is more in-depth and high quality than what can be found on the internet, and it would be so useful to be able to find more of the same content.

I don't think there are many people who can answer this question, but anything helps. Perhaps there is somewhere a set of rules on how school books are written? Or something similar on some government website?

Submitted October 16, 2016 at 11:27AM by VoidFunction1 http://ift.tt/2e9Qwzd