Learning to read and write English is exceptionally difficult and many children find doing so very hard - despite some people's claims to the contrary.
I have brought the thread Phonics - basics in which I tried to explain what makes learning to read and write English difficult back to the top again, in case that is of interest or help to u. But u'll see that I have been repeatedly pounced on for doing so.
Reading difficulties are caused mainly by the letters/spellings which have more than one sound, such as the 'a' in 'an, any, apron' or the 'o' in on, only, once, other, woman, women. If u listen to your child read and look out for the words which cause them trouble, u'll find that they are mostly ones with one or more tricky letters.
Spelling problems are caused mainly by having to learn different spellings for identical sounds 'men - many; bed - said; much - touch'.
(I have explained it all in detail on a website and blogs.)
Young children try to be logical, and because English spelling is often illogical, they can get very confused by it. The majority get there in the end - mostly because of patient, kindly help from parents. Having a (now grown up) son who found learning to read and to spell correctly very hard I know that helping a child who struggles can be very trying. (I often had to stop, let him have a break for me to calm down and try again, sometimes not till another day.)
It's definitely worth perserving. Most children find learning to read and write English difficult because it is very hard - even though some children learn incredibly easily. But not many are so lucky to be born with the right sort of brain for it.