A few thoughts on the 2006 OECD report...
1) Some countries have official language(s) in which all government functions are conducted, including teaching in government schools.
2) Some countries provide numerous financial supports which may, unfortunately, in some cases have an unintended side-effect of providing a disincentive to do well in school.
3) Some countries may have nationally controlled education systems, while others prefer local State control.
4) Some countries enforce immigration processes with selectivity and controlled numbers of persons which their economy can assimilate and their schools can support... others may have open borders with no selectivity and no limit/control for number of persons.

Aside from the report indicating the quality of education per se, these and other factors may have an impact... resulting in apples-and-oranges comparison. Rather than focusing on who's at the top, it may be beneficial to consider variables at play, including motivational variables.

In the context of this thread, a few thoughts on inclusion and grouping for instruction... for anyone who may not already be familiar with these...
1- http://www.casenex.com/casenet/pages/virtualLibrary/gridlock/groupmyths.html,
2- web search on Gentry Total School Cluster Grouping TSCG (one current link is http://nrcgt.uconn.edu/newsletters/spring964/),
3- http://journals.sagepub.com/doi/full/10.3102/0034654316675417.
4- book: Total School Cluster Grouping (TSCG), 2nd ed, 2014, Gentry.
5- book: School Cluster Grouping Model (SCGM), 2008, Winebrenner/Brulles.

A few posts upthread seemed focused on special ed disability... the USA has laws protecting persons with disabilities... summarized well by the helpful advocacy website wrightslaw, for anyone who may need assistance/direction with a special ed disability issue.