Does any of the examples below remind you of one of your students?
When student A reads individual note, she can recognize it pretty quickly. But when she reads music, she can't seem to put it together.
Student B has a tendency to memorize music. Once she knows how the music sounds like, she plays by memory and no longer looks at the score. As a result, her playing is missing details on note level
Student C has never been able to learn how to read music, he says that he has tried many times and If the letters are above the notes he can read the letters, but take them away he is lost.
I have a student D who has taken almost 10 years of piano with me and claims that she can’t read notes takes her the entire nine months to learn a piece. She depends on her ear, plus I write in a lot of notes for her.
Student E rarely looks up at her music when playing piano, he has good ears. I tried to teach him by ear, that didn't work since he couldn't remember it all and he would always end up guessing the notes instead of playing the pieces.
Student F always gives me an attitude, and I'm not quite sure whether she's pretending to read the notes or if she really gets it.
If the answer is yes, the problem most probably falls under one of the following categories:
The teaching approach: This is probably the first and most important reason why a student can’t read notes. Filling up the sheet with finger numbers or note names is only one example. Student C seems he falls in this category.
The student is an auditory learner: Probably the teaching approach is very good but the student is an auditory learner and this is how learns best, by listening and not visually by reading. As the term implies, auditory learners learn through listening as their main way of learning. Students B and E are good candidate.
The presence of a learning disability, examples are: Dyslexia, Dysmusia (musical dyslexia), Auditory Processing disorders or other disorders. Student A might fall under this category if you dig deeper.