Also, I do personally think it's hard to tell a bright kid from a really bright kid unless you're spending a lot of time with them and/or are unusually observant. I know a lot of kids who have been tested for GT who did not get in, and a lot who did (since DD is at a magnet where they only take kids in the 99th%). There is a big group there where I would have to say I just could not have predicted which way these kids would go. They probably are all in the 115-140 range.
Did some of those 115 kids look really sharp as toddlers and young kids? Maybe, yeah, and some of the 140 kids might have looked behind. My own daughter looked more "out there" as a toddler than she eventually tested, though I'd hardly say she's plateaued. Meanwhile my son didn't look nearly as precocious and now looks a bit more scary-smart. Time will tell. They're both basically in the "smart enough to do whatever they want and need to keep a careful eye on it" group, but not the "so smart we're really in trouble and school isn't going to work" group.
Personally, I think the tests are blunt instruments at best, but do serve a valuable purpose in sussing out unknown areas of really high ability and unknown areas of challenge. They provide additional info, but day to day experience is invaluable.
