Military households and the dependas that inhabit them aren't the stable footing you are imagining. The worst marriage stories I've heard happen under those circumstances.
The claim here is that the military families are /so much more stable/ that it explains their kids (collectively) performing better than every other state in the country.
Obviously the military provides some sort of economic lower bound. But it also applies a pretty harsh upper bound, and has all sorts of other effects that you would expect to push the mean down.
