Firstly, for all who say bucking isnt that dangerous, I've had a shattered wrist, two concussions(hit hard enough to break my helmet and give me a concussion), 3 cases of whiplash and a cracked tail bone from being bucked off. Training a horse not to buck from the ground up is the way to go.
He's probably also aware of the problems that come from over-protecting kids and not letting experience be the teacher.
I'm all for not over protecting kids, but their is a thin line between an 'experience' and stupidity. A young girl in our area this year got on a horse, I beleive with her families knowledge, that had been known to buck. She came off wrong and was dead before the ambulance could get there.
Sorry, but a 12 year old riding a known bucker, that is nearly immpossible to catch or bridle is silly, this horse needs some good training and a vet check to rule out teeth/pain issues.