I will also put my five copies on "born" literacy.
Years up to 12 stretched to any printed word, read absolutely everything that comes to hand, even obviously adult books, which sometimes did not understand at all (not porn, but simply designed for the mature mind). The result - no problems with spelling at all, with punctuation - only in very difficult sentences. In school, I was constantly getting pills for ignorance of the rules, the teacher didn't care that I wrote everything right without a hint, while the pimples depend on difficult words, looking for the right rule. And in the universe the teacher called it "linguistic sense".)