 Kim enrolled at Daegu High School in 2005, but he transferred to Jeju Tourism High School (the only high school in Jeju-do to have a baseball team) after the 2005 season.After sitting out the first half of the 2006 season as required under the Korea Baseball Association rules for transfer students, Kim subsequently became the top right-handed starting pitcher at the high school level, hurling a four-hit complete game shutout with 13 strikeouts on June 30, 2006 in the first round of the Golden Lion Flag National Championship.Kim became the first Korean high school pitcher ever to pitch a 10-inning no-hitter on July 14, 2007 in the second round of the Daebung Flag National Championship.