Many of us have no problem reading the notes of a masterpiece. We can certainly learn it note by note. If luckily the piece does not have more than four flats or four sharps, we might get through one page after half an hour. Then you go for a water break and have a snack and when you come back to the piano, you realise you do not remember most of the notes you played before.
Did you have the experience above? Or do you find your piano students are having such trouble...