Of course there are sad situations where a child gets sick, or injured or abused or stops being compliant enough to take tests.
But for the most part I think that really what happens is that a large enough number of the kids who are hard to perceive as gifted in the preschool or elementary years suddenly 'grow into themselves.' I'm guessing that this is why the DSY program wants a 150 for the WPPSI, and only a 145 for the WISC. And kids in the middle school years can 'run of test' to really show how unusually gifted they are. So there is a very real reason that IQ scores tend to be less unusual as the child ages past 7 years of age - but the child isn't less smart, only 10 to 20% less unusual, see?
((Could a number fan actually ballpark what the real numbers above should be. I pulled 10-20% out of the air - I tend to be quite intuitive with numbers, but please don't quote me!))
But given what you have described about your babies, TT, don't expect having 20% more company to change your daughter's LOG.
As for fizzling out, if a child sits in a classroom that is so far below their readiness level that it actually shames them, and the make an internal promise to themselves to totally hide their gifts at school and concentrate on the social side, but spend their time at home pouring all their intensity into some activity that isn't societally appreciated - are they still truly gifted? I would say yes. Did they fizzle out? Sure. That's why we work so hard here to find fun and challenging ways for our kids to learn how to learn and learn how to handle challenge - so that when they finally get in a situation that suits their readiness level they will have the basic skills in place to work well there, and the comfort level with working hard to persevere.
Some people mentally simplify this question by talking about 'gifts' vs. 'talents.' A talent what one gets if they truly develop their gifts well. That's why it is the 'Davidson Institute for Talent Development.' All the kids there have gifts, because that's how they were selected. Will all of them develop societally recognized talents? Certainly not. Why else would there need to be a group to promote this?
I keep saying societally recognized talents, instead of talents, because how many of us have developed our general gifts into being talented parents (many) and how many of us get much external recognition for it? (far fewer than is deserved)
Parenting is a hugely important thing, both personally and to society, and being a good parent is a fine way to use prodigious gifts. Do we live in a society that agrees with me at this exact moment in history? Not that I can tell. Do some of us who identify as 'just a Mom' feel like we fizzled out? As my grandfather used to say: I wish I had a nickel for everyone who said yes to that question. I know that if I didn't have a job outside the home where people tell me I'm clever every day, and you dear ones, that I'd be seriously confused about my talent of parenting - and I'm an amazing parent.
LOL@me! How did I get this far off topic?
Love and More Love,
Grinity