Associated Board of the Royal Schools of Music
Exams can be taken on many different instruments.  In nearly each case there are eight grades, numbered from 1 to 8.  For example, someone who has learned the piano for a short while may take Grade 1 once he or she can play pieces such as a simple minuet, and play a few scales with separate hands.  By the time they take Grade 8 they will need to be able to play movements from sonatas by composers such as Beethoven, play all 24 scales in various ways very fluently and be good at sight-reading.