That is the first time for me to hear it. I wish someone can shed more light on it. My DD has a relatively low PS partially due to perfectionism. She didn't get 99.9% on her reading achievement but did get 160 on math. The psycholigist told me that it is due to the low reading test ceiling. Her reading grade equivalent level is 12.9. And she only missed on question and it put her at 99% instead of 99.9%.
I remember reading here once that it can be hard to get the PG score on achievement tests if WM and PS are on the lower side. I wonder if there is any research on that.
