Sure, but If you can improve your IQ by studying, that suggests that this number isn't some hyper-objective thing we should treat as immutable or that it's even a true reflection of the person's total cognitive abilities.

I'm not saying that IQ is useless or anything, just that we should take the results with an appropriately large grain of salt.

You can improve your score by getting better at the tests and improving exam technique and maybe go from (picking numbers out of my arse) 115 to 120. You can't go from 90 to 120.