My older boy is hearing impaired. he is an okay speller, but below what you would expect given how bright he is- I assume that is due to the hearing loss.
He has an almost photographic memory. What I do is give him 10 spelling words on notecards each week (downloaded from lists on the internet). We flip through them daily for a week. After 2-3 days of just looking at them, he can spell them correctly.
After a year, that is like 450 new words he can spell. I expect he will never be a phenomenal speller, but this way, he will be on the map.
Writing out the words is a good way to remember them also.
