Musical flashcards have been around forever, and are still very helpful...especially for the visual learner.
metronome part. Take the student's set of flashcards (whether made, or bought). Shuffle them and then set metronome at a slow tempo (slow enough for the student to have some success). Flip the flashcards to the beat of the metronome and if the student gets the card correct, place it into one pile and if the student is incorrect, place it into a second pile. When you run out of cards, pick up the second pile and review them again, this time w/o the metronome and giving hints if needed. If the flashcard set is small enough, and if time allows, shuffle the set and go through it again w/ the metronome to see if the student can remember those once incorrect cards.
Once there is success, raise the tempo of the metronome. Teachers can do this at the lesson or parents can do this at home. Older students can even go through the flashcards on their own (perfect for those long waits at dr. offices or long car rides).
Why does this work? It helps the students make decisions more quickly and not "have to think about it". This comes handy especially when they need to know a symbol or staved note in the middle of a piece of music and don't have the time to sit and figure it out the long way.
So go start flashing!