I don't really think that IQ could tell you how smart the person is, you can get better at it just by practicing. My sister is just 14 and in few years when she learns more don't you think she'll score much higher than just 156(now she knows what the test is like).

Unfortunatly, the Q in IQ is stands for quotient. Thus, as she get's older the test effectivly gets harder ( not really )
If she stayed as smart as she was now, and waited a year, her IQ would drop.

Also practicing for an IQ test rarely works. :D