He started working part-time since the 2nd year of middle school and, because of this, his school grades suffered.
Remarkably, Kim Hyun-Joong was able to save nearly 100,000,000 won (roughly $87,000 USD) from his part-time jobs by his year school years. During Kim Hyun-Joong's late teen years, he felt the subjects he was learning in high school were useless for his life and, consequently, decided to drop out of high school.
Often, during this time, he wound up at the police station for fighting. By the age of 18, Kim Hyun-Joong performed in a youth band named "Aksuseu" ("악서스"), which was formed with Kim Hyun-Joong's Catholic Church friends.
They were quite popular in his local neighborhood of Songpa-gu in Seoul. While working part-time jobs, Kim Hyun-Joong was cast by the boss of an entertainment company, but the boss turned out to be a con man.
After getting away from that management company Kim Hyun-Joong was introduced DSP Entertainment and, after auditions, became a member of boy band SS501.