LMom, I agree that there is a difference in size of hands, but my point is when you roll a chord you can add many notes in the hand span. You can skip several notes, and it is taught even to 4 year olds as a technique. They just need to hit the lower note first. It becomes second nature after a while.
Also, when I was talking about "reading notes" I didn't mean by site reading a flash card set. That is rote memory. I also didn't mean playing out of a second or third level piano book. I was refering to the ability to open up a piece of music at intermediate-advance level (The Piano Guild has a different means of levels) and playing it correctly without error. In other words, reading music as easily as reading an intermediate book.
I have taught teens (2 of them) who have improved greatly in just 6 months, from going to little reading to intermediate level. Later, they reached advanced. They are also much quicker to go through to the advanced theory books. Teens can be amazingly quick! It has to do with with the motivation and time put in. (One wanted to become a keyboard player for a band, and worked hard on mainly theory.)
I have also taught gifted 4 year olds, who go through the books and songs, but they don't go anywhere near this level in 6 months. They take quite a bit longer as each level increases. Counting and rhythm for intermediate level playing is usually a challenge until they are quite a bit older. This holds up younger kids. They can even get frustrated about the counting at the middle intermediate level and quit at this point, due to the repetition involved in perfecting it. Having someone under 6 reaching advanced level, isn't very common, but of course it does happen, it's really rare though.
Anyway, I was just offering some suggestions for the little guys. They are so fun to teach! I like seeing them enjoy playing and performing. I hate hearing when they are having meltdowns at home.