When i was younger my old man told me once i hit 10-10 in the area he wanted me to hit then i could go. That made me practice harder and harder. I think its more or less if hes ready mentally too. Take him along with you bow hunting for a year so show him its not always whats seen on shows. Explain to him the Do's and Don't out in the field after a situation. Then when he can explain situations to you then he may be ready. Thats just the way my dad and brother did it for me.