IQ test are also not completely accurate for those that are gifted and have a learning disability. Kids that are gifted + LD'd may not even be put in gifted programs because their IQ scores are too low, but too high to put in an LD program, so they are stuck in normal class rooms where it isn't a good fit for them. Imagine being just as intelligent, if not more so, as the students in the gifted classes but denied access. That's what IQ scores do for some of those kids.
IQ test tend to work for gifted people that answer questions quickly and those without lopsided talent. If you are gifted + LD, or gifted but have really slow processing speed, then IQ test will not identify you as really that gifted, despite being so.