The old adage of "you can't study for an IQ test" either isn't valid, or the WISC isn't a true "IQ" test.
It isn't valid. The publishers are extremely careful about letting too much information get out about the test, for this reason. What's really true is that you *shouldn't* study (specifically) for an IQ test because this will invalidate it. Practice certainly can make a difference, and my guess is that this is likely to be especially true for young children because there hasn't been time for so much divergence between the specific tasks of an IQ test and the tasks one encounters in every day life. It's not just the obviously "knowledge" based components, either, I bet. For example, I'd wager quite a lot that a few minutes a day spent practising digits forward and digits backward, tests on which full details are easily available, would improve one's score dramatically over a few weeks. (In fact, given that I'm now never going to take an IQ test, I have wondered more than once about trying the experiment.)
ETA: Weirdly, you hear the same thing about problem-based maths competitions: "you can't study for them". Of course you can, and if you want to do well, you should!
