Like most boys his age, Melvin Yeoh used to pick fights in school, not knowing how else to channel his teenage angst.
That was 14 years ago.
Today, the 31-year-old uses his experience to help troubled teens by teaching them self-discipline in the octagon; the eight-sided ring used in Mixed Martial Arts (MMA).
Yeoh, who teaches Geography and Sports Science in a school in Johor, has been the head coach at his father's MMA gym since 2006.
"I used to fight a lot in school and often got penalised. Because of this, my grandfather enrolled me in a martial arts school.
"At first, I thought that learning martial arts would make me a better fighter in school. Instead, it taught me self-discipline. And I realised competition is the best place to channel all that angst," he told the New Sunday Times.
Born in Perlis, Yeoh was 13 when he first picked up taekwondo and later progressed to muay thai, where he competed in many tournaments and won a few titles.
However, his martial arts days were put on hold when he pursued his studies at Universiti Teknologi Malaysia.
Upon graduation, Yeoh was posted to Johor Baru, but as there were no MMA gyms there then, Yeoh decided to start his own by gathering some troubled teenagers and taught them basic MMA.
"The lessons were conducted at the back of my house. But as the number of students increased, my father and I started the Ultimate MMA Academy JB.
"We just want to get these kids out of trouble and to channel their aggression into the sport.
"Slowly, more and more parents sent their kids to our gym."
Aside from self-discipline, Yeoh also teaches his students to be independent by doing some part-time work to earn pocket money.
"It is better to give them a chance to find a purpose in life. If they are neglected, they may end up in a life of crime and become a nuisance to the community."
Some of his students, aged between 11 and 18, have taken part in several MMA tournaments in Kuala Lumpur and Johor.
MMA is the fastest growing sport in the world with big events such as the Ultimate Fighting Championship (UFC), K-1 World Max in Japan and Singapore-based One FC.
Unlike boxing or muay thai, MMA is not tied to one style of fighting but is a mix of two or more styles such as wrestling and Brazilian jiu-jitsu.