In general, IQ tests are supposed to reveal potential, while achievement test are made to reval what a child has accomplished. For effictive advocacy, it's great to show that your child has already learned what is being taught next year AND that she learned it not because you've kept her chained in the basement with flashcard, but because her potential is so unsual, so this trend is likely to last. Weirdly, the best known achievement test - WJIII, doesn't say much about how far above level a child is performing, and reports it's scores in misleadingly named 'grade equivalents.' It's a very good test, but we're still waiting for the tests that can be feed into a computer and a 'This child belongs in this grade' type report can be spit out of a computer.
Do you live in 'ACT land?' - if so the Explore (aimed I think at 8th graders) might be familiar to the local school folks. A third grader scoring at the level of the average 8th grader will speak volumes. You want to speak whatever language the hear-ers will understand.
If you live in a state that uses the SAT, then you are sort of out of luck until your child can sit through that...age 12 is 'average' around here, 10 isn't that unusual, but 8, well, only a few kids can get much out of the experience at 8. (You can always get a practice book and take a sample test at home for fun to get an idea...)
Another approach is to get 'end of year' tests in various subjects for the next few grades up and show them what your chld can do in those areas. Clear and convincing 'evidence' of above average achievement is better than a test that shows 'potential' any day, right? Both is best. If your school does MAP testing that should be an easy way to talk about how 'alone' your child is at present.
WISC IV and WJ III are wonderful, and can help you understand a more detailed picture - if all goes well, but various schools will react to the scores in various ways - depending on the school or the personel at the school at the moment. If you are at all unsure of what you are seeing (and who wouldn't be?) it's a terrific investment.
Hope that helps,
Grinity
