TCS Daily - Race, IQ and Education: "The concept of IQ works like this: there are tests that one can give a young child which allow that child to be assigned a percentile relative to other children of the same age. Many of these tests seem explicitly designed to measure intelligence. However, other tests, such as the Stanford Marshmallow experiment or tests of reaction time, are not what we would intuitively think of as intelligence tests, and yet results on these tests correlate well with IQ. The main finding is that a child's performance on one test will correlate with his or her performance on another test."
A fascinating article about g and how our educational system is totally screwed up because they are looking at the wrong problem with the wrong solution.