The IEA’s Trends in International Mathematics and Science Study has some interesting results.
Singapore, Korea and Hong Kong are tops, all over 600. The midpoint is 500 and NZ is 486. Bottom is Yemen on 248.
Korea, Singapore, and Finland are tops, all over 570. The midpoint is 500 and NZ is 497. Bottom is Yemen on 209.
Hong Kong, Russia and Finland are tops, all over 568. The midpoint is 500 and NZ is 531. Bottom is Morocco on 310.
The graphs are worth looking at, because they show the distribution for each country also. You can also see the results for 2001 and 2006 as well as 2011.