Teaching qualification testifies that you are not just proficient in dancing, but more importantly in teaching (the correct technique in an effective and safe manner). These are qualities prospective students and parents look for closely.
Contrary to college dance degrees which focus on performance, teaching qualifications earned by examination (often with examination boards and qualifications award bodies) deal comprehensively with theory, practice and teaching ability in specific dance genre.
A number of associations/examination boards exist, often as national bodies, while several operate internationally. Standards and syllabi they set vary, but are largely based on that set by associations founded in England back in the 1900s.
International associations conduct examinations and connect dancers around the world. The International Dance Teachers' Association Great Britain for example is represented by more than 6,000 members in some 55 countries. Other examples include the Imperial Society of Teachers of Dancing London and the Royal Academy of Dance.
The qualifying path is as follows:
Step 1: Study and practise according to the relevant syllabus requirements
Step 2: Entered into examination by a professional member
Step 3: Sit an examination, during which you demonstrate dance proficiency and answer questions put by the Examiner. An examination generally lasts from 45 to 90 minutes, according to level.
Step 4: On passing the examination, be admitted to the association as a professional dance teacher (at Associate, Licentiate and Fellow level as appropriate).
If you want to judge at competitions, a teaching qualification is a pre-requisite.