Terrace,
A couple of general thoughts:
AE and GE should not be taken as actual functional or instructional levels. This is not a criterion-referenced test, where, hypothetically, the scores are anchored to mastery of skills demanded or expected at certain age or grade levels. It is a norm-referenced test, based on standing in the population. The AE and GE are derived from the raw score or adjusted raw scores (W score, in this case) obtained by the 50th %ile of the standardization sample at that age or grade. It doesn't even distinguish between getting every item right in sequence, and then suddenly meeting the discontinue criteria with six in a row incorrect, and a very different scenario, where there are incorrect items interspersed with correct items, such that the most difficult item completed correctly is a much higher-level item than in scenario one. These two profiles generally have quite different meanings, but will result in the same AE, GE, and standard score.
If you take a representative sample of 30 year-olds in North America, you will find a highly divergent range of applied mathematics skills among them, even if we restrict our sample to the middle 68 percent (+ or - 1 SD from the mean) of performance levels. Think of the ordinary 30 year-olds you know. Some of them are quite facile with math, as evidenced by their engineering or finance jobs, or their expert bargain shopping. Others can't calculate change at the cash register, and panic at the idea of balancing a checkbook (both skills that require math no higher than third grade level). So there are two issues here: what is the real-life meaning of math applications at the 30 year-old level, and, does the AE score accurately indicate performance or instructional level at this age level?
It's also not clear to me from your account if his ceiling item was at the 30 year-old level, or if his AE score was at that level. Two very different situations, as the ceiling rules for the WJ are a bit different from some other tests, in that the examiner must administer complete pages, and also meet the six-in-a-row wrong discontinue rule. This means a child could, hypothetically, get five items in a row incorrect, then one correct, and then eleven more incorrect, at the ceiling, which would mean, that, for the sake of two raw score points (not that much, IOW), 16 incorrect items were administered, of which the last eleven were wrong. This might result in a highly-inflated estimated age/grade-level of the last item administered.
Which is why I would caution against placing too much weight on the AE and GE scores.
