Basically, they are normal kids, but as the mystery progresses, and they find out more and more about the weird new teachers, they start to develop certain skills and abilities.
I suppose at this point you have to ask 'why use the Gatewatch at all'? I mean if they are normal kids from a normal school with no knowledge of the greater MTG universe then you've basically just got a bunch of kids (and supporting cast) who happen to have their looks inspired by the Gatewatch & Co. If that's all you're looking for then that's fine and dandy but I figure the point in making them the Gatewatch was to draw upon the Magic universe, you know?[/quote]
You are right to ask, and for a while, I couldn't properly put into words what my motivation was in so radical a departure from canon while wanting to use the same characters (sort of). It mostly boils down to two things: juxtaposition and defying expectations.
First, juxtaposition creates comedy by contrasting the known personae of these characters with a comparatively mundane setting. Think of Darth Vader managing a grocery store. Why use Darth Vader if he isn't the dark lord badass we know and love? Because it's so out-of-sorts that it creates a logical dissonance which makes it more funnier.
Juxtaposition: imagine a sinister galactic theocratic inquisition, but their spaceships look like pizzas.
Second, when we have preconceived notions of how these characters think and act, the fun comes in both playing to and against these expectations. We expect Gideon to be the somewhat stubborn, but noble and well-intentioned herp. So, you play up that he's a real standup guy, but then introduce that he's also easily startled by raccoons or something. (Plus, and this is probably just me, but I want to see Gideon Jura with a bad teenage mustache.)
And none of this is to say that things mightn't get more like the canonical plot as things go on. Using Scary Go Round as a comparison, things get more and more outlandish as stories introduce more disparate elements of supernature into the setting. There's no reason an Archie-type Gatewatch Gang couldn't become more fantastical as it progresses.