My 5year old son writes very slowly in school when writing school work and at home when doing homework.  His teacher says he's a good student; he raises his hands, participates, answers questions.  But when it comes to writing he's so slow that he doesn't finish his writing assignments and in turn has to do it for homework.  The only thing his teacher says is to practice with him.  

We have been practicing with him since summer school this summer (req for new students by the school).  He wrote slowly then and still writing slow.  What I have observed at home with his writing is that he daydreams a lot. So, He'll write a few letters or a couple of words and then he gets to daydreaming.  

How can I help him with this situation.  My son is a very smart child and I swear I don't say that because he's my son.  I've had people come to me and accolade at how he can hold steady conversations with grown adults.  He soaks up information like a sponge and can retain it.  When it comes to the writing thing, though...he needs help. what can I do to help him?

Thank you in advance.