Ahh, one of our favorite topics in our house! DH and I were just having this one...
In our school, they look at all kids and have gifted pull-outs for K-5. Then they have the top kids take the SCATS in fourth grade--if you score real well, then in 5-7 you go to a gifted program 1 day/week. DD10 qualified for this, but we've known she was smart and the school told us she was gifted bakc in first grade.
DS8--well, what can you say? Boys! We love him to death, we think his IQ is higher than his older sister's, but he doesn't have as much "focus" at this stage. I believe he's what I term "Holy Crap Gifted"--he's the one that the teachers say they've never seen anyone like in 25 years of teaching, and in K the principal even told me he's concerned about DS getting a proper education in our public school. When he was in K, they checked his reading--he got 95% at a sixth grade level..at age 5. They sent him for additonal testing, but they just gave up--he could read anything they put in front of him, and comprehension was off the chart, too. But...we haven't had him tested. We keep him in the public school, for now. Here's my philosophy: he's happy and learning. He has friends and is developing socially. He likes his school, his activites, looking forward to starting thrid grade. I'm trying to raise a self-confident, independent adult, not impress people with his IQ scores. It's working for us, for now. I don't think testing will help him, and likely won't even give an accurate result, because he may not want to. Frankly, I think his brain scares him sometimes--he just understands stuff way beyond his years, and that's tough for a kid. So for now, I accept him as he is, no further evaluation necessary. YMMD--this approach isn't for every child. I'd be more inclined to test my youngest (DD2) in a few years--she appears to have her brother's IQ without the emotional baggage. If she has more focus, she may need more academic challenges earlier on. But for now, I'd settle for potty training!
Anyway, my general philosphy on testing is, if you have a concrete reason for testing (qualifying for special services, disagreements with the school, etc.), it may be useful. But you have to ask yourself if the result is really important to your child's future? Yeah, part of me would love to know where DS really falls--but I'd also like to know if #4 is a boy or girl, and won't find out today! Oh, well. And I would also mention that, although I don't believe that DD10 is quite as stratospheric in IQ as her brother, she has a great work ethic and positive attitude which will serve her better than a few IQ points either way.