Welcome!
Not speaking for DYS at all, as I am merely a member of the public, and have no official standing:
But I would suggest contacting them directly and requesting that they advise on appropriate use of his testing data for a DYS application. My personal reading of the requirements is that the grade level to use as a reference should be the one in which the child is currently enrolled, or has just completed (if between school years). Your child appears to be enrolled in second grade, with single subject acceleration to eighth grade. That would make him a second grader (since he hasn't received instruction in all subjects past the second grade). It would seem reasonable that the standard of "meet or exceed" as a second-grader would be met if he meets or exceeds the third (or fifth!) grade criteria. It also seems likely that the chart doesn't show 2nd grade because there aren't enough 2nd graders in the data set to justify a robust cutoff score.
