Onara Taisō or Exercise for Farting, is a song that originated from the popular Josei (comics aimed at young women) manga Nodame Cantabile. [link] The series has been running in Japan since 2001 and is mainly about the relationship between its two main characters; classical musicians Megumi Noda and Shinichi Chiaki.
The manga has been remade into an anime, a live-action TV drama (which you can find online), and a live-action movie (also online). In 2006, the comic won an award from the New York Public Library for Books for the Teen Age.
All the kids in the clip are dressed like characters from the series.