Reading and writing difficulties can be caused by different underlying issues- it could be dyslexia, dysgraphia, language processing, phonological awareness deficits, working memory, etc. Sometimes it is none of those things and the child is still developing their skills. When completing a language/literacy evaluation, several areas need to be assessed to determine where the weakness lies; this is called a differential diagnosis.
Depending on the age of the child, I assess the following areas: phonological awareness, phonological memory, rapid naming, phonics/decoding of single syllable and multisyllable words, spelling/encoding of single syllable and multisyllable words, letter formation, sound/letter sequencing, written expression at the sentence and paragraph level, reading fluency accuracy and rate, vocabulary comprehension and use, language processing and auditory processing, and reading comprehension.