They haven't even been taught decimals in third grade yet. So how would that work for a child who doesn't know what 55.33 means?
I find it hard to imagine a gifted third-grader who's never asked and been told what a dot in a number means or what that little 2 up there means, and for a sufficiently gifted child that's all it takes. We have a thermometer at home that measures temperature to 1 decimal place of celsius, for example, and I remember puzzling during the stage when DS (aged two? I'd have to look it up) might still read "18" as "eighty one", about why he'd never make such mistakes with "19.3". Similarly, seeing something sold in m^2 is enough exposure to exponentiation for some. I don't dispute that afterschooling or good differentiation makes it easier for a child to score high on an above level test, but I'm with Sweetie and others: it isn't a necessary condition.
