> The educational aspect of schools is (mostly, but not entirely) redundant to the resources available for free on the Internet.

I think this overestimates it. What I've found from internet 'learning', myself and others (and the students I used to teach) is that there's more often the illusion of learning than any actual learning. Let's not equate watching a YouTube video and thinking we understand it to actual learning. I've been victim to that myself when trying to learn pure math, and with kids it'll certainly be worse.

And the same issues will carry over to any online textbook too. Teachers are there to actually assess what the kids really learned, not what they think they learned, or what they can google to get past the next question on their assignment. The internet just fosters the illusion of learning (and let's not even get to critical thinking from it).