Which is why an IQ is useless. If it can rise then it is not really measuring intelligence. Rather it is measuring what you know so far. Which explains why kids from better income families have better IQs.
And yet people treat IQ as a constant. Glad I decided never to let a single number define me. To all you that believe the IQ is important I say ...
Whilst you can probably influence your IQ by working your brain really hard every day or lower it by doing a lot of drugs I doubt it is really that meaningless as it does tend to correlate well with success.
However I'd be curious to know how it correlates with lifetime income once you control for family income. I assume this has been researched.