Kalamies

Maybe you could teach them lines (EGBDF) and spaces (FACE) or, if you're teaching them both G-clef and F-clef EGBDFACE. This encourages reading by lines and spaces and discourages reading by calculating, which is slow and seems to be quite intuitive for many beginners. I have taught this (informally) to three people. 8 and 10 years old got it, but the 16 year old didn't get it...