When he was in primary school, Wong Joong Rong, now 16, would often walk around the classroom during lessons or play with the stationery on his desk.
He knew he should be seated and focus on the lesson. "I still walked around. I couldn't help it," he said.
His teacher was so stressed by it that he once tore one of his books in front of the class.
Joong Rong was diagnosed with ADHD or attention deficit hyperactivity disorder at the age of five.
His mother, Madam Leow Bee Bian, told his school's allied educator about his condition, but was not sure if his teachers knew about it. Allied educators help those with special needs.
But he never complained about his teachers. "When I picked him, he was always very bubbly," the 48-year-old accounts officer said. "I'd ask him how his day went and he'd say it was okay."
He became more aware of his condition as he grew older. "In Secondary 1, I was very naughty and my teacher scolded me a lot. I talked non-stop during class and I didn't like it when my teacher told me to stop talking. I'd argue back."
Now a student at ITE College West, he has learnt to better manage his anger and impulses.
The change came when he was in Secondary 2. He said: My counsellor got me to think about my mum. So I tried to study hard so that she'd not worry so much."
From Secondary 3 onwards, he started on his homework right after classes so that he would not forget about it as he has poor short-term memory.
Counselling opened his eyes. He would put himself in his teachers' shoes and make an effort to control his impulses.
It also helped that he found out he was not alone. He said: "From social media, I saw that other people also have this problem."
The responsibilities given to him in school - as a class treasurer in Secondary 3 and then as class vice-chairman in Secondary 4 - also helped.
He said: "I had responsibilities so I'd do the work. I am not the type to stop halfway. I'll finish the task."
He also represented his school in basketball.
Madam Leow said that as a child, he was very active and playful. "He would play with his toys and my kitchen utensils. He couldn't stop. When he was hungry, he wouldn't tell me. He'd continue playing."
Reading to him was not an easy task. She said: "He wouldn't allow me to finish reading a whole page. He would turn the page."
Joong Rong has come a long way from those days. He was a merit winner of the Ace Teen Award at the third Asian Congress on ADHD, held here in May.
The Active, Creative, Energetic Awards recognise children and teenagers with ADHD who have overcome challenges to realise their potential, as well as mentors who have made a difference in the lives of children with ADHD.
Joong Rong said: "I still talk in class but I try to talk at the right time and I try to lower my volume."