Good question Sandy, I would say Keith has to be one of the best people to answer this with the amount of top class kids coming from his gym. The hardest training lad in my gym is 14 and has his 1st fight in 2 weeks under UKMF junior rules (no head contact). If we want them to learn Thai scoring as it is implemented at the moment as per Tony Myers judging courses etc then no head contact and training them accordingly is good for developing the Thai style scoring (focusing on kicks to the body, knees and good dominant clinch). I grew up as a kid in the sport and trained and sparred full head contact, unfortunately this didnt prepare me for junior competition with no head contact so I was easily outscored by fast body kickers when I had been focusing too much on boxing, head kicks and low kicks.
I actually like no head contact for novice kids but once they progress to elite kids level like TJ Everett from Keith's gym they will be seriously held back by not fighting head contact. Its down to the instructor/coach to be responsible and look after the kids safety but also not hinder their progression if they are ready!