I don't understand what info this gives either. DS was given the 2-5 version and scored almost 260 on math but my understanding is 260 is the ceiling and 246 is the 99th percentile for his grade so I don't know what that means about how high above grade level he is, or how high above the 99th percentile. Pretty useless, IMO, other than it telling us he is advanced which we already knew.
Its function is to gauge growth for the grades it's geared toward, not determine advanced instruction levels. It's useful for gauging being advanced, just not for true mastery, due to limited number of questions. One option is to request the winter and spring testing be on the 6+ version, due to being at that high level, close to the ceiling. It is likely there will be a drop in RIT initially when switching (the higher the RIT, the wider the margin of error, and the larger the point variance, like 12+ points).
You may want to show the school this document about transitioning test versions.
https://www.nwea.org/content/upload...ath-6-plus-Transition-Guidance-MAY15.pdf
