At 6, my son could sound out simple words with much effort.
At 7, he could read simple words fluently and would have to sound out bigger words.
Now that he's 8, he reads almost every word that he come into contact with in level 3-4 books without needing to sound them out.
I voted 7+, because before that, he was unable to both sound out and comprehend, and to me, that's not really reading.
My daughter will be 6 in April and while she knows the letter sounds,...