i was like your student. my fourth piano teacher finally got me to read. i was motivated because i had finally realized that the works i wanted to play would be forever beyond my reach if i didn't learn how to read. i was playing a brahms intermezzo by ear, but i was becoming impatient with how long it took to learn pieces in this way.
my teacher took me back to flashcards and open staves with random notes, basically, took me back to kindergarten. she also made me count, and the constant demand to be aware of which beat i was on in the measure helped me learn to read as well.
then i was given very basic pieces to learn, pieces i could learn in a few days, easy enough for me to sightread at my sightreading level, though far below my technical and musical abilities.
i worked my way through burgemuller and several other books of short and easy pieces.
then she had me get bartok's microcosmos and sight read a couple of those a day. i had to play as slow as it took to play everything correctly, including dynamics, and then play it twice more to get it up to tempo.
meanwhile, she kept me entirely away from more advanced repertoire. i was only allowed to learn beginner repertoire. she wanted to get me hooked on being able to play lots of new pieces, instead of my old pattern, which was to work for endless months on one challenging piece.
finally, we worked on interval recognition by using a methodist hymnal. i had to sight read a hymn a day, and i was not allowed to look at my hands. i had to play entirely by relational distances on the keyboard.
now i can read.
it was painful, and it wouldn't have worked if i hadn't learned the necessity of it. at least in my case, but then, i am stubborn.