IQ ≠ ATAR
IQ = GAT
The way which IQ is tested is totally different to what GAT tests though. Anything which has an essay and language component is unlikely to correlate well with IQ. That's not to say those who do well on GAT aren't 'smart', but they're testing totally different types of intelligence. From how I see it, there's multiple forms of intelligence and IQ only tests one of those really...
EDIT: Simple example, autistic kids. Most are going to gun any IQ test but do terrible at any language-based test.
However, autism is associated with a form of mental retardation and many really do struggle with parts of the test and so have on average quite a low IQ (lower then average person), but can be considered geniuses with other parts 'booksmart' with maths/science, struggling horribly with anything else.
it really varies, haha, sorry to add this in, just wanted to make a note ><
But this really does show how someone who is considered a genius in their field, can actually have a really low IQ. So does that make them stupid? No, it just makes the test itself stupid for that person...