A common problem with music lessons seems to be that the child can play at a different level than they can read.
I have many students who can pick out a nursery rhyme or popular song, play it hundreds of times for fun until it is very fast, and then perform it endlessly. However, if I put a simple piece of music with an unfamiliar tune in front of them, they struggle to recognise the notes and stab at any note, guessing, until they hopefully hit the correct one.
We use note-reading apps, regularly practise sight-reading, play with flash-cards, and use the old fashioned “ALL COWS EAT GRASS”, “EVERY GOOD BOY DESERVES FRUIT/FUDGE/FOOTBALL/FERRARIS” memory rhymes to aid in learning where the notes go on the staves. And still, many of these students (and many of them boys, whose aural skills are so much sharper than their visual) continue to struggle with simple note-reading.
I don’t have the answer, so please feel free to comment if you have a strategy or idea that you have found helpful!