Top 20 High School Korean Dramas

Top 20 High School Korean Dramas up to year 2015.
(I have restricted the list strictly to High School. Hence those which have university/college life in more focus would not be in the list. Eg : Playful Kiss, Heartstrings).

Song Used : 'Serendipity' by 2young from The Heirs OST
(I don't own the rights to the song or the pictures used. They belong to the respected creators.)