\I'm not sure what the point of the grade-equivalents on those tests is, unless it's to sow confusion...I mean, who cares how a 12th grader would do on a 4th grade test? And did they make a bunch of older kids take the tests so that they could establish norms?
This is only true for certain achievement tests. STAR testing adapts levels and gives harder questions if the child is getting questions right, so it does not mean the child was only tested on grade level. STAR math covers at least through pre-algebra. Achievement tests like the WJ and WIAT have questions that include high school level material, so a GE of 12+ refers to grade level tested, not what a 12th grader would do on 2nd grade material. Similarly, the Explore test is an 8th grade level achievement test. Scoring at the 99th percentile compared to 8th graders reflects mastery of 8th grade level material, even if the child is a 5th grader. There is no GE returned, but the achievement reflected is based on 8th graders, not the age of the test taker.
Results that mean "an 8th grader would test this well on a 4th grade test" can be seen in grade level testing. I've never seen GEs on such tests, but my kids have never taken ITBS or that kind of test.
What a GE means for an individual child when tested on higher level material is anyone's guess!
I've seen a WJ score for >18th grade level for math for an elementary kid. That's just a silly number. There isn't any material on the test beyond what most students cover in high school and that is way too brief to demonstrate anything other than superficial familiarity with the concepts. There certainly are not graduate level math questions.
Mostly, I think GEs are best ignored. For tests with more than a few questions per level (Explore, ACT), comparing a kid's scores to how older kids score may be worthwhile. For tests with just a few questions at each grade level, it's not very helpful to get a grade result. Schools care about whether a child has mastered the local curriculum, so end-of-year finals are usually better at figuring that out.
