First, I believe your DS' school personnel have made the classic mistake of confusing "above average high achiever" with "gifted".
I just had to say that...
IMO it sounds like you "might" be looking at some type of learning challenge because of the gaps, what you've said about the writing and homework (though like ZenS said he might need to be engaged). It could be that your DS' strengths are carrying his challenges along just fine. The comments about not getting an IEP are very true.
I think only time would tell. He is still young. I'd just keep an eye on him, see if his writing progresses, try to research other techniques to help him with this than the schools use.
I'd also make sure you help him discover and develop any strengths he has outside of school (I'm always going on about that!) There is alot of difference getting into 3rd grade and then 4th + when it comes to writing expectations so you have time if indeed there are challenges there.
