i started both of my kids out when they were less than two. I made them bows made with a single piece of nodes on bamboo with a handle glued on the belly side. They were faster than the little fiberglass models. On his second birthday, my son got a large boxing rabbit blow up thing from his gram-ma.  We showed him how he could box it and it would rock and not fall down. He seemed confused and left. A few minutes later he walks into the room, bow and arrow in hand and before we could stop him, he shot it in the heart with his bow and killed it. My mom almost had a stroke laughing while the blow up bunny deflated to the floor.  Moral of the story? You can start them young, but you have to keep a close eye on them.