Shoot! I was hoping someone with better knowledge would pipe in about GEs, but I'll take a stab as it was explained to me. Grade equivalent on some tests reflect how a child in that grade would score on the test. So if you gave a 10th grader a first grade test, and the 10th graders on average scored a 98, then a first grader scoring a 98 would be GE 10th grade.
But, my understanding is the WJIII is not that way. It actually provides material at that level (10th) to the child and if the child does well on it, the GE is 10th grade. Of course it has limitations in that there are few questions at each level and can't possibly capture the whole of the grade. It just means that your child can answer one or two 10th grade questions. Still somewhat useful to know.
Looking back at the detailed score report from DS's WJ-III Ach testing, there are two breakdowns, one with grade equivalents and one with age equivalents (there is a good deal of narrative information prior intermixed with tables, but these are the summary sheets I'm looking at). For each tested area, there is an "EASY to DIFF" column, with a lower and higher number for each area; the reported grade or age equivalent is in a preceding column, and falls somewhere in the middle of the range, although not at the average (it actually seems to be usually a little below the average).
If I had to take a complete guess, the DIFF value is probably at or very near the upper bound of the level of questions that he was able to answer correctly at all. I don't know what would feed into a determination of the EASY level, but total or near-total mastery seem like good bets. Grade and age equivalents might be calculated using the range, but in my seat-of-the-pants good-guessing layperson's opinion more likely not, and are probably keyed to a particular mastery level too (50%? 85%? It's impossible to tell from what I have). It's all over my head, and I don't have time to muddle through the numbers with a calculator.
