I too use interval size to teach note reading. It is a real struggle because the public schools still use acronyms for the lines and spaces. But when a student is strugggling with a song, and I show them how they could read it with step up, skip up, same, step up, etc, and they see how much quicker it is, I usually can convince them.
Dana:
Yes, and I have found that refreshing the concept frequently is very helpful. When I ask them to WRITE the notes (say, a tricky-to-read measure) on our little lap whiteboard, sometimes they say, "Ohhh... I didn't notice that."
Down In the Valley is an old-fashioned song with sweet lyrics and a strong melody. Resting around Middle C & using just 2 chords, it makes a fine duet or solo!
Short aria Nel cor with piano accompaniment in the keys of Eb, F, and G! This pretty little aria is perfect for students just venturing into classical music.