Complicated question that I'm trying, without luck, to find the answer!

My DYS son is 9 and in 5th grade (skipped). His RIT scores haven't moved a whole lot and the Descartes Goals printout I'm getting from our homeschool adviser is relatively thin. For example- his Word Analysis and Vocabulary (from last winter) says 231-244. On the Descartes printout, it is literally blank for 240+

Is there a benefit/detriment to having him take the 6th and up test? Right now he takes the 2nd-5th test. Our homeschool charter is under the impression that there is no ceiling and the questions go out of level (which I agree.) But it appears that the Descartes goals stop at a certain range for the mid-elementary test. When I look for the 6+ subtests online, there are differently titled subtests and Descartes goals.

Is anyone more familiar with this test, able to explain how the continuum works?