IATEFL

International Association of Teachers of English as a Foreign Language

British-based international association.

http://www.iatefl.org/

IBO

International Baccaleureate organisation

The International Baccalaureate Organization (IBO) is a recognized leader in the field of international education, encouraging students to be active learners, well-rounded individuals and engaged world citizens.

http://www.ibo.org/

IELTS

The International English Language Testing System

This is an internationally owned and globally recognised direct English Language assessment system. It is primarily used by those seeking international education, professional recognition, bench-marking to international standards and global mobility.

http://www.ielts.org

IMO

In my opinion