My dad started me out shooting when I turned four. Small game hunting when I was eight, and deer when I was 12(State Law in Pa, which is the only state we deer hunted in at the time). It's an individual basis I suppose, depending on the kids maturity and responsibility. I dont think any age is to young to start shooting, as long as it is well monitored of course. But hunting requires judgements that many kids are not ready to make.
-Jake