First, understand that IQ tests can be biased and can shaft minorities. Second, they are tools and are only as good as the person making use of them.

Third, eat right, exercise, live right, etc. Performance is impacted by health and even supposedly high IQ people will perform worse if they are sick, short of sleep, etc.

IQ isn't a useless concept, but I'm somewhat well versed in the history of IQ tests, etc, and it's got a lot of issues with it.