I just started ground driving my dad's 4 year old filly. She has longeing basics down pat, as well as tarp, obstacle, cone, bridge, teeter-totter work, etc.. She is used to being at my shoulder. It took her 20 or 30 minutes to figure out that I wanted forward movement when I was behind her. She got herself wrapped up in the lines several times, as well. It could be a disaster in the making for someone that rushed the horse or wasn't reading body language.
I just think for a 10 year old child, there are much more effective ways to establish leadership with a horse. Nevermind the fact that I don't see the advantage to ground-driving a horse that is as well-broke as Ace seems to be.