Fischer's retail race skis (GS & SL, adult & junior) are delivered with 1 degree base bevel & 3 degree edge bevel. Atomic standard configurations are the same. The Fischer tuning guide recommends going to .5 or 0 degrees on the base for SL (for kids especially, I would only recommend this if the racer can work the ski well enough).
I work with K1 & K2 (K1 is 11/12, Canadian equiv to J4 I think?), and if my 11 year olds have never skied with an edge bevel before, I recommend starting with 1 base/2 edge for GS and SL. (If their skis are already at 1 & 3, I won't change them, but I'll pay attention to how the racer manages.) For the better skiers, I would start right off with 1 base/3 edge, and work towards reducing the base bevel to .5 for SL.