I had the same question as Dottie when I read it and came up with an explanation similar to ColinsMum's. The main takeaway is that when a child scores around 245 in reading on the secondary test, that should be considered their lowest possible score. Their actual score could be a little or a lot higher, but it's impossible to know without using a different test.
I wonder what the math RIT ceiling for the secondary test is? 265??
I think there's a similar effect with the primary test somewhere around the 210 RIT level.
Here's another interesting post about the NWEA MAP.
http://kitchentablemath.blogspot.com/search?q=nweaThe probability density graph is interesting as the bell curve flattens and standard deviations get wider as children move up in grade level.
When I looked at the SD on the national data, they seem to increase every year up to 8th grade then decrease. I wonder if this is due to the test ceiling on the upper end of the curve?
