Sang-ho is an ordinary high school student. His dream is to enter the military academy under the influence of his father who is an army colonel. As entering high school, he became friends with Jae-gu, Chang-bae, Kyung-chul, Hong-kyu and Sang-sik. They grouped a soccer team called `Tiger`, building up friendship by playing soccer. Sang-ho and his friends ran into group of fight with seniors, these incidents made everybody in school to misunderstand read morethem as they were serious group of gangster. When Sang-ho gets becomes close with a girl whose boyfriend is a boss of another school`s gangster group, things are going worse.
Although Gangster High deals with high school gangs, its depiction of violence is no less fierce than any Jopokyeonghwa, Korean gangster films. However, the film never romanticizes violence. Sang-ho is not romantic at all, and he turns into a cruel fighter when violent actions are unavoidable. As in his previous film A Whispering Corridor, a horror film of fearful, nightmarish girlhood, director Park depicts reckless teenagers living in the world without compassion through cruel, cold eyes.