Looks very good to me. Letter reversals and spelling will correct--unless you are at a school that doesn't believe in inventive spelling, in which case it might need to be taught before skipping. The sentence structure is good. It would be good to see him string together several sentences. I think first graders usually end with a conclusion from what I remember, like in the sentence where he says, "so no".
There's the writing process which looks like he is fine. Then there's the writing phonics, getting all the letter sounds in there. If every syllable is represented by a sound and you have some 3 syllable words, I think it's good enough.
Here's a link to info:
http://www.readingrockets.org/looking_at_writing/first_grade/writing_sample_1/ If you aren't sure, go into school and look at the writing on the wall. (Or ask an expert, which I am not)
