If you look at the correlation between the IQ between parents and children (young children in particular), there is not much of a relationship. It's very weak. So there are plenty of low IQ parents with high IQ kids and vice versa. The relationship is stronger if you compare teenagers to their parents. It seems counter-intuitive, but it is what it is. I'm suggesting that the rate of development for young kids varies so much, that could explain some of the difference, as well as differences in environment. The child who is given puzzles to play with is going to do better with block design on the WISC. So even if a trait inherited, it doesn't necessarily show up in early childhood. There is also research showing that if an IQ test is given to a preschooler, there is only a weak correlation with their score even a few years later. So the scores can change dramatically over time even in the same child. Personally I think it's useless to even give a young child (under 6 or so) an IQ test unless they are one extreme or the other. It may show how they are functioning at that moment, but it's not very predictive.
Most of the kids on this forum are highly gifted with scores over 130 or 140, and you will not see as much fluctuation with scores that high, or variance between them and their parents (my hypothesis at least).
