Dr. Richard Askey, via a kind email (PDF):

TIMSS is an international set of tests on mathematics and science which is given every four years in grades 4 and 8 to a sample of students, and occasionally for a sample of students taking advanced mathematics and physics in their last year in high school. All of these will be given in 2015.
The following useful link gives access to the released TIMSS-2011 items and the scores different countries made on these items.
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One interesting fact is that among the 42 countries which tested 8th grade students, Finland had the highest percent of students who picked answer A and the third lowest percent correct, Chile had 11.7and Sweden had 14.4 percent. The Finnish result is likely a surprise to the people who have praised the Finnish school system for their results on another international test, PISA. However, one group which would not be surprised are university and technical college mathematics faculty in Finland. See an article signed by over 200 of them which is on the web at:
http://solmu.math.helsinki.fi/2005/erik/PisaEng.html