Did your teacher refer your dd for testing because she felt she was gifted, because she felt she was underachieving, or because she had concerns about her academic performance? If she was referred for testing simply to see if she was gifted, because her teacher felt she was, and as long as everything is going well as far as you can tell with school etc - I wouldn't put too much thought into the difference between her ability scores and her achievement scores. The WJ-III achievement tests are brief, and they cover very specific tasks - for instance, math fluency will test how many math problems she can solve within a short amount of time, and using handwriting to show her work. Her score could be influenced by a number of things that aren't related to ability - exposure to concepts, whether or not she tries to hurry or is motivated by the test being timed, how quickly she writes, prior practice with math facts, etc. My take on achievement tests (jmo) is that tests such as the WJ-III Achievement tests etc are very useful for sorting out the impact of learning challenges and strengths, but if you want to measure achievement that is more relevant for understanding grade placement, tests such as MAPS, ITBS, Terra Nova etc are more useful (for parents at least!).
The one thing you've noted that I'd want to know more about is why the difference in GAI vs FSIQ - that *can* be a signal of a challenge that impacts academics, and if that was the case, there might be something to the discrepancy in ability vs achievement scores. My ds, for example, is dysgraphic, and it shows up as a higher GAI than FSIQ (due to impact on Processing Speed subtest scores) and shows up in scatter in his WJ-III Achievement scores. If you have any concerns or are wondering about whether or not there's a challenge, I would look closer at the subtest scores - are they consistent between subtests or do they vary between subtests? (look at this both on WISC and on WJ-III).
I'm sorry I can't help answer the question re how often at age 7 is achievement consistent with ability, but fwiw, I suspect that's a question you could ask of the person who tested her.
Best wishes,
polarbear
