Sometimes, if you ask an inattentive or dominant horse to canter with authority they will give a buck but then canter instantly whenever you ask them. However, I have never thought of head shy as a similar thing, and combined with the bucking under saddle and avoidance it is likely bad. It sounds like the trainer taught the horse to stay away from humans and made the horse lose trust. He thinks a hand coming for his face means pain. Since you seem to be implying that the horse had a nervous disposition to begin with, this probably made him more nervous. With fearful horses I prefer there to be more positive teaching than negative. Punishing a nervous horse can make the problem worse.
It sounds like now the problem is getting worse and you may consider dropping the shows until the horse comes to trust humans more again, and finding a more experienced trainer who knows how to deal with timid horses would probably help you. A fearful horse in the more chaotic environment of showing combined with 12 year old is a recipe for danger.
"The trouble with the world is that the stupid are certain and the intelligent are full of doubt"
Last edited by roro; 07-17-2010 at 05:55 PM.