I think observing is a great idea! Our school requires it. I started Suzuki at 6 as well. So much easier to start at that age! But there are benefits to starting younger and it can be worthwhile with the right teacher and program. Our program is great and so fun for young kids.
I do totally agree with Chyrs' comment about not really being further ahead in the repertoire starting earlier. With both my kids and with friend's kids they hit a point where it clicked and then they were able to move at their own good and consistent pace through new music. It's just painful to trust in the process until you hit that point!
Hitting that point has a lot to do with small motor, listening skills, practice skills, and not necessarily length of play.
Chrys - fiddle music is so fun! Can't wait until we do that.
