I didn't mean to push you to rewrite the fic! I was just surprised that Trevelyan's age, which I think is only at the top and not in the story itself, didn't entirely jibe with his reading abilities!

I know that there are kids who read at three; I just don't know any personally, except that now I'm remembering the son of a friend of mine might have been reading store signs that early, particularly "Exit."

I was more musing about what would happen if actually taught one's small child ciphers along with reading. The kid might just pick it up. A simple substitution cipher might seem no more arbitrary than the alphabet we have: if you learn "A" makes the sound /a/ and /æ/ and /aI/, and "B" makes /b/, but your older brothers are doing ciphers, might you add a rule that looks like: sometimes "A" means /a/ or /æ/ or /aI/, but sometimes it means /b/—if your father likes a simple shift substitution? Good musicians can transpose instantly; they read a note that says "A" and then play a "C" or whatever without even thinking, "It says 'A,' but I've transposed, so I have to play 'C'"; they just look at the transposed note and read "C."

(Am I even making sense?)