I think the most important thing is to keep anyone young or old INTERESTED in whatever insturment they want (or think they want) to learn. I started on an acordian at about 8, but I really wanted to play harmonica so I didn't play that long. In Jr high I played flute and became first chair because I then got to play the piccolo in the marching band and it was the lightest insturment to carry. Then in college I picked up the Guitar which I still play and a bit later the fiddle. Throughout all this I kept at it only when I could play the music that interested ME. My wife on the other hand still doesen't play the piano because her teacher only wanted her to play classical and she wanted to learn blues.