Why does IQ shift Drastically?

by Samuel
(Not Given)

I've taken three professionally administered IQ test, each from Wechsler at different chronological ages. WPPSI at age 7 and 1 month, WISC-III at age 7 but six months, and at 18 and 4 months.

The results of each test were in three different classifications and standard deviations.

The first test, I achieved a FSIQ of 138 as a highly gifted individual (WPPSI), the ESE board said that because I was in the upper limits of the age group for the test, that I should have been given the WISC-III. I was given the WISC-III and achieved an average FSIQ score of 108 which stated that I didn't qualify for ESE.

On my own initiative, based mostly on the opinions of others-I still possess faculties of a gifted thinker --even at ages two and three had an abnormal attention span to complete 100 piece puzzles, a profound vocabulary, interest in music, and really high fluid reasoning skills that results from playing with puzzles and blocks, and having to deal with numbers--so I consider myself above average at least. I freely took another I.Q. test, the WAIS-III at age 18 and 4 months and the results were FSIQ of 120.

So, lets look at the scores respectively, and this is my theory: The WPPSI was most accurate, however, because of the second testing with the WISC-III, I was not placed in the environment that cultured the type of brain activity of gifted children, thus, although my IQ was and still is high (120), it isn't as high as it would have been if placed in gifted--IQ seals around age 7, which made the testing process difficult to begin with.

But my question is, excluding Flynn's effect and keeping in mind the Theory of Cognitive Development, how and why does IQ shift so drastically?

138; 108; 120

That's dropping 30 points, 2 SD's down, then back up another 1.5 SD? Consider the previous test scores, and my age, is it likely to reach a MENSA level?

Mind you the uncommon shift of previous scores?