I have a pet theory that I like to carry around with me (and I bookmarked on my computer before the hard drive crashed). If you think of a brain cell as being like a computer that is connected to other brain cells by ethernet cables, the insulation on the cables is called myelin. There's been some research that suggests that the the greatest impact genetics or your physical body has on intelligence is through the quality of this insulation. For some reason, I find this thought rather comforting.
I'm a teacher with little experience in gifted education, but I have run more meetings to determine eligibility for Special Education than I can count. I do tend to think of giftedness being similar to mental retardation, because both represent remote corners of a normal distribution, whose difficulties come about because they are so far from the norm.
I also think of cutoff scores as being a line arbitrarily drawn on a bell curve. There isn't a gap on that line that makes the people on one side noticeably different from the folks on the other. There are plenty of people who happen to be very close to it. The line doesn't have much meaning in the real world, in other words.
If a public school looked at a IQ 2 points higher than mentally retarded in this day and age and declared that student was not eligible because they didn't meet the cutoff, it would be in a world of trouble with state and federal law. For one thing, 2 points on a standard scale is a very small difference that might disappear if you happened to take the test on a different day. For another thing, they'd need to do another test whose name eludes me at the moment. I think it's called a Functional Assessment--the Vineland is one example.
Now, the laws for SpEd have always been stronger than the laws regarding gifted education, but having a single, hard-and fast cutoff score is just bad practice. Data from a variety of sources should be considered.
My older sister also missed the cutoff for the gifted class. She's a now a medical doctor in charge of training medical residents at her hospital. In the past, she's been chief of staff at a different hospital. If she was tested in this day and age, other factors besides a cognitive score--like her superior task commitment--would probably be considered, and she would probably qualify.
I'm going to suggest you google "3 Ring" and "Renzulli", and that you try to get your hands on a book called _Living with Intensity: Understanding the Sensitivity, Excitability, and the Emotional Development of Gifted Children, Adolescents, and Adults_ Daniels & Piechowski, ed.s
