Excellent lesson from Jersey Jazzman showing that the old tests produce pretty much the same distribution of scores as the new tests.
He has superimposed the green scores from 2008 on top of the 2014 scores for New York state in 8th grade reading, and basically they have almost the same distribution. Furthermore, a scatter plot shows nearly the same thing, and that there is a nearly perfect correlation between the old scores and the new scores, by school.
Read his article, which is clear and concise. I don’t have time to go into this in depth.