The TIMSS 2011 study involved 63 countries and 14 benchmarking entities:

Armenia Indonesia Oman United Arab Emirates
Australia Iran, Islamic Rep. of Palestinian Nat’l Auth. United States
Austria Ireland Poland Yemen
Azerbaijan Israel Portugal Benchmarking Participants
Bahrain Italy Qatar Abu Dhabi, UAE
Belgium (Flemish) Japan Romania Alabama, USA
Botswana Jordan Russian Federation Alberta, Canada
Chile Kazakhstan Saudi Arabia California, USA
Chinese Taipei Korea, Rep. of Serbia Colorado, USA
Croatia Kuwait Singapore Connecticut, USA
Czech Republic Lebanon Slovak Republic Dubai, UAE
Denmark Lithuania Slovenia Florida, USA
England Macedonia South Africa Indiana, USA
Finland Malaysia Spain Massachusetts, USA
Georgia Malta Sweden Minnesota, USA
Germany Morocco Syrian Arab Republic North Carolina, USA
Ghana The Netherlands Thailand Ontario, Canada
Honduras New Zealand Tunisia Quebec, Canada
Hong Kong SAR Northern Ireland Turkey
Hungary Norway Ukraine