Yes chay, that's exactly the point I was making.
Though to your (excellent) points indigo, I still think it should be easy enough to notice something unusual about those kids too, as long as one looks carefully enough. They may not develop as quickly or as well as children from more affluent and/or educated families, but the spark is still there and may still shine through, as long as you have an idea of what it might look like. I'd argue that it might be just as easy to identify a child who uses her imagination to create an elaborate world of her own, or a child who can outsmart her parents when she's three years old, as long as you pay attention.
That said, I certainly think it is a tragedy for any child to be left behind, gifted or not. Imagine what a world it would be if every single individual on the planet could reach their full potential!
The following is a completely irrelevant and personal segue but I finished before I realized:
I might point out that I was one of the lucky ones. Neither of my parents finished high school, they never once brought a book into our household (until my mother started reading the odd romance novel by the time I was in my teens), and they never once checked to see if we had done our homework (let alone reviewing it with us). And that was far from unusual in our blue collar small town.
Yet somehow, I managed to find my happy little place in the world by reading every book I could get my hands on (though it was mostly Archie comic books at the time!), hiding my marks from my friends (so they wouldn't think I was a "nerd"), and just cruising along with other interests (friends, parties, sports and boys). Once I got to university, I learned to study, got top marks, and went along my merry way. Though I can't imagine how differently it might have turned out if I'd had a LD, or motivation problem, or whatever.
By comparison, our boys are being raised in a very enriched environment. Our house is full of books, we are constantly exploring the world (whether through travel or with a nature kit around the neighborhood), and we want to impart as much knowledge as we possibly can to them. We also expose them to music, theatre, sports, etc. Gifted or not, they'll get all the enrichment we can provide for them.
And quite frankly, I don't care how well they "succeed" in life. I just want them to have a thirst for knowledge and be happy (in whichever way they define happiness for themselves). Though I must admit that I am secretly very pleased that both of them have expressed an interest in science!