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."
Old Joe Clark piano music for beginners is a winner! With goofy yrics, a step-wise melody, & great rhythm, it's a fun solo or duet. Bonus: it's easy to play!