We saw a similar drop with the WISC-IV over the course of one year. At 7.5 dd10 was around 148, if I recall correctly. At 8.5, she was around 128. We used different testers and the second one essentially told us that dd's abilities were "fluctuating." She also noted anxiety as a possible reason for the drop.
We had the WIAT-II achievement test done at the same time as the second test and a counselor dd is seeing now tells me that the WIAT scores are more in line with the first IQ than the second. The current counselor is leaning more toward, like Dottie said, the idea that the "truth" may be somewhere in between but she tends to think that dd is closer to the first score. I think that part of what is leading her that way is that, even with the big drop, dd had ceiling scores (18s, 19) on parts and she feels that moderately gifted kids usually score more in the 14-15 range.
In her instance, her scores qualify for a GT id at school either way b/c all they look at is the verbal index on the WISC for a reading/language arts id. She was at the 99th the second time and at the 99.7th the first on that index. Other tests are used for math and other ids and they won't consider full scale IQ or GAI for an id for some reason.
