I don't think you can 'go too far' in English so far as basic reading and writing is concerned -- once a child wants to be able to read for itself you can't stop it. The motivation of being able to have your own stories whenever you like without having to pester grown-ups into reading them for you took me into "Swallows and Amazons" before I was seven (I remember thinking how ridiculously babyish Roger was, when he was supposed to be older than me!), and most of the rest of my parents' childhood literature thereafter.
And the prime motivation of being able to write was that I didn't have to dictate my stories to my mother to write down for me any more.

Attempting to hold me back would have been pointless -- and very cruel, even if it did mean I'd basically finished the primary school reading curriculum before I started. (The teachers simply gave me the liberty to take anything I liked out of the school library instead of the approved reading scheme books, and let me sit at the back and read while the other children were being given flash-cards and cut-out words to take home -- oddly enough that didn't affect my popularity in class at all but earned me admiration.)