Don’t buy into Mensa. Christopher Hitchens took them apart years ago; one of the stupidest men I have ever known (although a good bridge player) was a member. I think IQ tests are accurate but I wouldn’t administer one to an adult with low self esteem.
I agree with he esteem comment, but I'm not entirely sure about the accuracy - or at least what exactly they measure. I think its really hard to develop an IQ test that is not also (or primarily) an aptitude test - like the SAT. At that point it doesn't measure what you ‘can’ know, but what you do know. At any rate, I've done well on standardized tests, and it's helped me in life, but I have lacked the ability to protect myself from malicious and aggressive people - which is also an aptitude/talent. We all have something unique to bring to the dance.