I'm not sure what your definition of "worked with" is but I first took classes in the 5th grade at a visual arts magnet school so 10+ is a good general answer for me in any manner. I've been taking pictures of family trips and sites we visited on the way (we moved alot) since I was a little kid though. Once I finally got my own camera that took decent pictures I became much more able to practice what I learned from the classes, although not as much as I'd like.