How many of the Japanese being tested aren't Japanese? (well Japan won't bestow immigrant citizenship on many people anyway)?
How many illiterates in the American sample came here illiterate and are now also illiterate in English because of bilingual edumacation?
Some schools here tried to cook the books with “superior testing” results by excluding these or those students.
I wouldn't doubt that there has been a dumbing down of Americans. I wonder how many other countries are under reporting their new economic refugees who live in unassimilated neighborhoods.