There's no shortage of unique concepts in the world of K-pop and Afterschool are no exception. Working on the basis of an 'admission-graduation' system, this girl group take collegiate music to a whole new level. Debut single "Because of You" topped multiple charts when it was released in 2009. Albums such as Virgin, Playgirlz and Dress To Kill have made the group the K-pop force they remain today, with their songs meandering between youthful innocence and sophisticated sassiness. Delve into the best of their back catalogue with our handpicked collection.