Reading this thread I cannot stop myself from writing of my own experience on this subject.
I have taught the piano for 30 years but in the first 15 or so years I always taught at a high level and had no experience of teaching even 5 or 6 year olds. But then I found myself in a situation where each year I had at least 10 new students aged between 4 and 6. I have to say that initially I found this extremely frustrating. However it forced me to develop a piano method which was especially designed for the 4 to 6 age group. Recent experience has showed that it is quite suitable for three year olds as well.
The method developed as my experience with these young children grew over the next 15 years. These children gave me the best possible feedback – I worked out the method with and for them. Now some of my most enjoyable experiences result from teaching these children, who learn piano in the same way as they learn to speak their mother tongue. At this age, and even earlier, appropriate connections are being made in the brain and it turns out that this is a particularly good age to start. My youngest was 2 and a half and I teach very many 3 year olds.
The approach is based on using animals to represent the musical notes Cat for C, Dog for D etc. so it is not necessary for the child to be able to read or write. It combines singing, improvisation, finger exercises, rhythm exercises, ear training, note reading etc. You can find more information on these techniques for teaching very young children at
www.dogsandbirds.co.uk. This method is now being used by hundreds of teachers and is proving to be very successful.