Assessment gap

K1 got her results from a standardized test over the summer. She did pretty well. One thing that surprised me about the report was the following:

In one sub-test she was in the 72 percentile when normed against "Independent schools" which I read as private schools. But when normed against the national norm (which I read as including public schools) she was in the 95 percentile. This tells me that the gap between the achievement of private and public school students is pretty large - larger than I had expected - which was no more than 10 percent at the 50-75 percentile range.