i've always wondered how the optional subtests work, but don't follow everything i've read on the web concerning this. My son has a very low coding score relative to the rest of his scores, thus pulling down his FSIQ. No one at his school seems to know what a GAI is.. so I was wondering if we had him re-tested and had another test substituted for coding, his FSIQ would be better. is coding a test that can be "swapped out"?