Once you get past phonetics, symbol/sound relationships - the only metric that really matters for basic literacy is # of words read. Should it be challenging?

Once you get past phonetics, symbol/sound relationships - the only metric that really matters for basic literacy is # of words read. Should it be challenging? Yea, sure - but ten short books or two long ones doesn't matter a bit. They just need to read more. Source: I'm a k12 English teacher. The data that makes it into my hands almost always comes back to this point.