Actually, if you read http://pirls.bc.edu/timss2007/PDF/T07_M_IR_Chapter1.pdf http://pirls.bc.edu/timss2007/PDF/T07_M_IR_Chapter1.pdf , Massachusetts and Minnes

Actually, if you read http://pirls.bc.edu/timss2007/PDF/T07_M_IR_Chapter1.pdf http://pirls.bc.edu/timss2007/PDF/T07_M_IR_Chapter1.pdf , Massachusetts and Minnesota are also benchmarked independently, Massachusetts is #4 globally (page 4 of the pdf, 34 of the document). Also, the level is slowly increasing in the US and slowly decreasing in Singapore. Finally, a lot of countries are missing in these rankings, so these are not true global results.