You already have excellent advice, so I'll only add that for my son, he would have never written that much but would have edited down what he wanted to say to the least words possible so he had fewer words to get through. Had he dictated the story, even at that age, it would have covered several pages. When he had to write, it would exhaust him to the point of doing poorly at everything else afterwards. He didn't even see the red line on the left side of his paper so that often by the end there would only be room for one word because he'd drifted so far right.
He also had difficulty with speech, couldn't zip, tie, or button until 4th grade (tying in late 5th). He can't ride a bike. He was late to learn to swim.
He doesn't keep things in working memory, will forget the third step of an instruction if given three in a row, and loses things (doesn't "see" the homework in his folder, can't find a shoe despite it being visible if it is around other objects), etc.
So I guess I'd look at the whole of it - is it just hand writing or are there other things cropping up that seem "off" from what you'd expect?
