The back-story to these young teenagers with big lists is that they are often driven around by their birding/twitching parents and encouraged to join in as a sort of eye-spy game. This way, the kids don't interfere with the parents' pastime. (There was an illustration of this on the 'Twitchers' programme that was on TV a while ago.) Nothing at all wrong with introducing children to nature walks, but here we are often talking about long hours spent in the back seat of a car.
There are a couple of repercussions for this type of activity. The first relates to issues of child-development and parenting, but this isn't the forum to explore that.
The other repercussion is for the 'craft' of birding. There is a craft to birding and it is learnt through local birding and getting well experienced with the commoner birds, before scooting off to 'collect' the rarer ones. You need a good experience with, say, Dunlin before you can identify some of the rarer waders. You need a good experience with, say, Chiffchaff before you can feel confident with some of the rarer warblers. And so on. Even our 'top lister' Lee Evans would strongly agree with this and repeatedly makes the point.
Tom - I don't know you, but from what I've read, you are doing very well at developing birding craft on your local patch. Don't fear, are already a far better birder that all these 'infant twitchers' put together!
Stewart