Ultramarina, DD's output at five would probably have been LESS than that, but the punctuation and spelling would have been perfect for what she DID produce. Writing is also easily her weakest area academically. She would NOT have produced such robust writing at 4.5, in all likelihood. In fact, I have samples from when she was almost four, and they aren't as detailed or complex.
I think that there is a pretty wide range of "typical" for kids in K-2. I know a few kids who would still have been using phonetic, invented spelling for some words as late as late 2nd or even 3rd grade, though. It looks to me as though he actually KNOWS how to spell most of what he is using.... he's just really, really focused on the physical task of writing at this point, which is probably completely age-appropriate even as late as 6-7yo.
I'm guessing here, but solid 1st grade doesn't seem like a reach in any way.
