School 2015 premiered yesterday with young stars Kim So Hyun, BtoB's Yook Sung Jae, and Nam Joo Hyuk filling the leading roles. Many fans have been anticipating the follow-up to the popular series School 2013, which launched Kim Woo Bin and Lee Jong Suk to stardom, but did you know that this is actually the sixth entry into a long-running franchise? Since 1999, KBS has been using the School series to launch some major K-drama stars, some of which may surprise you!

First running from 1999-2002 with four seasons and then rebooting with School 2013, the School series has long been known as a star-maker, featuring virtual unknowns and turning them into some of the biggest stars in Korea. After the unexpected popularity of School in 1999, the follow-up shows became coveted roles for young up-and-coming actors, as fans anxiously anticipated who would appear as the next breakout stars. While many K-drama stars can call themselves alumni of the School series, here are 10 of the biggest names to walk the School halls:

1. Jang Hyuk (School, 1999)

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A cast member on the first School series, Jang Hyuk had mostly acted in music videos before this role. His next project after this series was the movie Volcano High, which made him a recognizable star.


2. Ha Ji Won (School 2, 1999)

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Ha Ji Won began acting in 1996, but her role as a troubled teen in the popular School sequel was her breakout moment, opening bigger opportunities for the actress.


3. Gong Yoo (School 4, 2001)

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Long before he was a Coffee Prince, Gong Yoo had his very first role as Hwang Tae Young in School 4.


4. Lee Dong Wook (School 2, 1999, and School 3, 2000)

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Lee Dong Wook actually played the role of Lee Kang San not once, but twice, in back-to-back seasons of the show.


5. Choi Kang Hee (School, 1999)

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The original School series was part of Choi Kang Hee's earlier filmography. She won a KBS New Actress award for the role.


6. Jo In Sung (School 3, 2000)

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Jo In Sung made his acting debut with a splash as the star of the third installment of the show, winning a Youth Actor award for his performance.


7. Bae Doo Na (School, 1999)

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The star who has made her name in Hollywood also made her debut in the first series. Like costar Choi Kang Hee, she won a New Actress award for the series.


8. Im Soo Jung (School 4, 2001)

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After making her debut in School 4, Im Soo Jung almost immediately began her illustrious film career. She has only starred in one other K-drama, 2004's I'm Sorry, I Love You. All of her other work has been on the big screen.


9. Kim Min Hee (School 2, 1999)

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Kim Min Hee was already fairly established as a teen star before the series, but this helped solidify her position, earning her a Youth Actress award at the KBS Drama Awards.


10. Kim Rae Won (School 2, 1999)

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Like Kim Min Hee, Kim Rae Won won the KBS Youth Actor award for his attitude-filled character in School 2. It was his second acting role.


Did anyone surprise you? That's not even all of the actors who appeared in the series! Do you think School 2015 will live up to the series name and catapult the stars to bigger and better projects? Share your thoughts in the comments! 

If you missed yesterday's premiere of School 2015, you can see it below: