re: What is the right age for teens to start weight lifting?

All of my kids train (except #4 whose 4mos). Train doesn't mean traditional weights.

I have a "slosh tube" I made for my son (7) that has gotten him pretty strong/stable. Take a pvc pipe around 3-4ft long, cap one side and fill it half way with water. Then cap the other side. Have him hold it in his arms and walk. The tube is relatively light, but the "sloshing" action forces a ton of stabilization.

This comes closer to what human children would naturally do (vs. free weights) if they weren't living in such a soft world.