It was a fellow prefect who introduced her to cigarettes and the pair always knew where to smoke in school without getting caught.
"I tried it out of curiosity. It was exciting to smoke in secret," said Siti who is now a Form Two student in a private school.
From one to two cigarettes a day, Siti's curious habit turned into an addiction.
By the time she reached puberty, she was spending RM15 a day on smokes, puffing up to 60 sticks.
The 14-year-old is now neither a prefect nor an athlete. Smoking had deteriorated her performance in school.
Siti is one of the growing number of teenagers seeking help at the Health Ministry's Quit Smoking clinics. She and 11 of her schoolmates are now "patients" of the Tanglin community polyclinic.
Siti has made good progress since she came to the clinic more than a month ago.
From 60 sticks a day, she went to five cigarettes a week, then one stick a month and now she is "clean".
Her expenses, however, have gone up. Where she once spent at least RM15 daily on cigarettes, she now spends close to RM50 text messaging friends.
"I wanted to get smoking out of my head. I did not want to think about lighting up, so I began to occupy my thoughts on other things, like boys!"
"I am now thinking more about boys and texting phone messages like crazy," said Siti.
But what made her decide to quit?
It was for various reasons -- death of her boyfriend, her health had suffered, but best of all, the school nurse caught her.
"My boyfriend, who was a year older than me, died of a stroke. He was a heavy smoker. Both of us were seeing each other for four years and all those times, we smoked together.
"Then one day last year, he suffered a stroke and died. I suspect it was due to his smoking."
It then dawned on Siti that it was not really "cool" to keep on smoking.
"A lot of things suddenly dawned on me. I was a straight As student. I was always first in the 100m sprint. Both these suffered.
"I also had problems sleeping, eating and suffered from constant backaches."
By then, Siti was a seasoned smoker. Not only that, her circle of chain-smoking friends in school had also grown bigger.
Siti decided to slow down and started cutting down on the number of sticks she burnt up daily, but it was too late, the school nurse found out.
"You are such a stupid girl," was her father's first response when he found out about his daughter's habit. Incidentally, he was a former district police chief.
Siti, the youngest of five siblings, was taken along with her schoolmates to the Tanglin community clinic.
Siti's schoolmate, Dean Aziz, read his pledge to quit smoking in a fast and monotonous way.
It was not convincing.
His school nurse, who was sitting in with him at the session, looked agitated.
"You really mean it? You must be serious you know," she said.
The 16-year-old just nodded.
The others in the group gave various reasons why they wanted to quit. Among the reasons were: " My girlfriend wanted me to quit, I did it for my health and family, to save money."
These students are from an elite school whose parents are VIPs, prominent businessmen and professionals.
Things are looking up for these teenagers. One month later, they have quit with the help of medication and counselling.
They are, however, still undergoing treatment.