Michelle is very resourceful!
Mahagogo, I mean that FSIQ, in a balanced profile (which appears to be more common near the mean), more closely approximates g. When the index scores are as diverse as they often are for GT pops, GAI more closely approximates g.
You can calculate GAI from subtest percentiles using Michelle MacGyver's method, but, as she notes, you won't be able to obtain ExIQs. Of course, that is no different than if you had conventional scaled scores, instead of percentiles.
Can2K, if a WISC-IV without PSI or WMI was administered, then the score you received was likely the GAI, in percentile form. Alternatively, she may have been assessed with the brief version, the WASI-II, which is a two- or four-subtest abbreviated version. If only two subtests were given (vocabulary & matrix reasoning), the most interpretable score would be the FSIQ-2. I wouldn't withhold anything from a parent, but I admit I would be a bit reluctant to put too much weight on the subtest scaled scores in that case, unless they were quite significantly different. The FSIQ-2 takes about 15 minutes, usually, and isn't an unreasonable individual screening option. Probably better than group CogATs and NNAT-2s. Plus, if you add testing within a few months, you can actually combine them with the remaining subtests of the WISC-IV for a complete battery.
Do our neighbors to the north not have some equivalent of FERPA? Down here, parents have a right to any individual student data on their children. (Much to the distress of publishers and most psychologists, parents can even demand to view the original test protocol, since it represents child products.) Although districts can make it very difficult to obtain them.
