To the Beautiful You (tv-series, 2012)

Goo Jae-hee lives in the United States and one day sees a track and field competition on TV, and becomes attracted to one of the high jump competitors, Kang Tae-joon. She begins to idolize the young athlete and eventually transfers to Korea to attend the same school that Tae-joon attends after he suffers an accident that could potentially end his career. There is a catch, however: Tae-joon attends an all-boys high school and Jae-hee must disguise herself as a boy to enter.