We had the same test results with my DS6 on the woodcock johnson....he had just finished K when we did the testing and it showed in both reading and math that he was on various levels of second grade but with the writing it showed that he was actually at mid K level and in some cases beginning of K in writing. We had taken him to get a full eval last year out of concern for his handwriting/drawing/fine motor skills and they diagnosed him with Dyspraxia. Everyone offered some great advice...we also used handwriting without tears and we use a special graph paper to help with writing...we are trying to look for a good keyboarding program so he can learn to type and are looking at getting a learning keyboard with a little bit bigger keys for him. His "writing" stories is amazing and will sit for me for an hour and make up his own book and have me do most of the typing...so there is NO way he could write all of the stuff that comes out of his brain so the teacher hasn't been able to see that he really can formulate ideas in his head and has a lot to write about he just can't get it down on paper.
My little guy is the same way with spelling as well...he can verbally tell me how to spell a word when he is NOT thinking about it or focusing in on it...but the minute he has to sit down and try to remember how to spell a word, he can't...I am convinced he is also a visual -spatial learner.

Here is the Dyspraxia website that I found a LOT of really helpful information
http://www.dyspraxiausa.org/