We weren't testing DS for giftedness but were investigating delays. So at 3.5 his score was 106 and at 6 on the WISC it was 126, with his non-verbal score being 141. I think his non-verbal score was around 118 when he was tested at age 3. At age 6, he had the test after taking about 5 other tests on the same day, so I don't know how accurate it was--it might be an underestimate. I have to say that when he was tested at 3 he wasn't particularly cooperative so who knows what his score would have been back then if he had tried harder. It's incredibly hard to test preschoolers. Some are very shy and others are hyper. If a preschool child is extremely calm and cooperative during testing, their score might actually be an overestimate because that child is being compared to all the very intelligent kids who score poorly because they are shy or hyper and don't test well, but are actually brighter.
I think there is research saying that scores can fluctuate a lot until a child is 8 or 9 because of poor test reliability with young children and also differences in brain maturation. Check out the book "Nurture Shock"--there is a chapter in there on giftedness and IQ testing. If a child tests at the extreme high end, they are probably not going to fall down into the "not gifted" range, though. Kids develop at different rates so an early-bloomer is not necessarily gifted and vice versa. My kid was delayed with just about everything and now his GAI is above the 99th percentile, meaning he has surpassed many of the kids who appeared brighter at age 2.
Here is a brief summary of "nurture shock"
http://nurtureshockmoment.blogspot.com/
