The hypothesis that MoodyMoody gives sounds plausible.
What I do in such a case is the use of BIG COLORED flashcards :
- the letters at the exact shape, rather thick. Make your pupil touch them and follow the edge at least 3 or 4 times. Then ask him to draw around the letter and associate the sound when he is touching the letter. You, then both of you and then him alone.
- then draw flashcards with specific sounds or syllabus (the most common at first).
- then put pictures and words you want him to learn.
- Make him put the sounds or syllabus in the right order to make the words you have just said then ask him to spell the same words with the colored letters.
- then use these words (for example articles in blue), adjectives in orange and so on as you will do for a jigsaw puzzle.
- I sometimes draw a train with wagons (with pictures on) to make the good order of the words in a sentence.
You can ask him to close his eyes when you are saying something - that way the brain focuses on the hearing.
You will repeat with the WELL separated words on flashcards. Very slowly at first, then a little faster.
Make the spaces between the words narrower.
Ask your student to repeat at first with you, then after you. Insist on the sound, then on the sounds associated with the written part.
You will need to repeat again and again but it may work as it has worked several times for some of my students.
I hope it willl work.