A friend of mine had children that went to Steiner schools and they weren't taught to read until they were 7, and he said they could read adult level books by 9.
It appears there's evidence that this is true in general[1] (though the author suggests they could go even faster if they updated their methods further)
I also remember reading in a Tony Buzan book his speculation that learning to read too early interfered with the, what he claims, is the natural eidetic memory potential in children. I don't have any of his books here to find the reference, unfortunately. Perhaps there's something in it, perhaps not.
I personally learned to read as early as I could recall (around four) but lacked much attention span to actually crack open a book then and found being read to more fun. Not as a matter of personal bragging but to point out that kids in absense of formal teaching methods may absorb many things.
Immersion learning is used and studied mostly for foreign languages but I wonder about how effective it proves in general for small children given vs trying to teach them actively and leaving them to observe it. It may be a fringe case technique when directly teaching them is ironically less effective or even more effective when it does work but unreliable.
I learned to read at a similar age, and quickly started reading (relatively) long, complex books. I have difficulty focusing on things, but I think the many hours spent on focused reading at an early age helped significantly; I would probably be in a much worse state now if not for that.
It appears there's evidence that this is true in general[1] (though the author suggests they could go even faster if they updated their methods further)
I also remember reading in a Tony Buzan book his speculation that learning to read too early interfered with the, what he claims, is the natural eidetic memory potential in children. I don't have any of his books here to find the reference, unfortunately. Perhaps there's something in it, perhaps not.
[1] https://theconversation.com/steiner-schools-should-adopt-mod...