They might share a birthday, but their very first encounter was far from friendly.
Former Tanjong Katong Secondary School (TKSS) student Marcus Tang, 18, recalls the first time he met Mr Clarence Tng, who heads physical education (PE) and co-curricular activities (CCA) at the school.
"I was in Secondary 1 then - he came to call me out of class, and scolded me for not filling in my CCA form," said Marcus.
Now, some six years later, he has nothing but praise for Mr Tng, who was his PE teacher in upper secondary and the year head for Sec 3 at the time.
Said Marcus: "We often had meetings because my results were very bad, and I had to be retained for a year in Sec 3. But Mr Tng never gave up on me."
The teacher would often give pep talks to the teenager.
"Repeating a year was a rude awakening," said Marcus. "I realised there were people who really cared about me, so I decided to change my attitude and, gradually, my results improved immensely."
He is now a first-year science student at Victoria Junior College.
Mr Tng, now 41, is closely linked to TKSS, where he has taught for nearly nine years. He is an old boy of the school, and his father, Mr Tng Hia Seng, was a former vice-principal there.
TKSS principal Dolly Ong said: "To his students, he's their life mentor and coach. When they find themselves at a crossroads, Clarence gives them good counsel."
Said Mr Tng, who is married to another teacher and has two sons: "The interactions with the students, the letters of affirmation we receive and the moments when students are able to see that life is more than studies - they are very fulfilling."
Mr Tng said he makes it a point to build a rapport with his students.
"It is important to hold conversations with them, structured or unstructured, formal or informal. Students are soon able to see things from your perspective and why you do certain things, and to cooperate with you. They are more willing to listen, share and trust you," he said.
"It takes time, many years."
Indeed, for a long time, Marcus did not believe Mr Tng when he said they had the same birthday - March 27. Marcus was convinced only recently when Mr Tng took out his identity card.
Laughing, Marcus said: "Looks like I will never have an excuse to forget his birthday ever again."