When Mr Aloysius Teo graduated from the Institute of Technical Education (ITE) College East in 2011, he considered ending his studies and entering the workforce.

He was already 26 then, and had worked for three years before pursuing his Higher National ITE Certificate in business studies (administration) at 24.

He wanted to support his family - his mother had been the sole breadwinner since his father died in 2003, and his brother is intellectually disabled.

Mr Teo sought advice from Dr Thomas Koo, 44, who taught him business modules at ITE.

"He did the typical business teacher kind of thing - pros and cons," said Mr Teo, who eventually decided to further his studies. His decision has paid off.

Last year, he graduated in the top 20 per cent of his cohort from Temasek Polytechnic with a diploma in marketing. Mr Teo, now 30, intends to study for a degree in criminology at the Singapore Institute of Technology.

Mr Teo wrote to the SG50 Give Thanks initiative of North East Community Development Council this year to thank Dr Koo, an ITE College East teacher since 2001.

Dr Koo said he was motivated by his own experience with a teacher. He had done badly in his O levels in 1987 and had to pursue his A levels as a private candidate, which he said was "devastating" for him. He said his teacher had "expressed confidence that I can do it".

Dr Koo also received thanks from Ms Amy Toh Yee Hong, another grateful student.

The 22-year-old had applied to study integrated event management at Republic Polytechnic but was offered wellness, lifestyle and spa management instead. She considered turning down the offer, but Dr Koo dissuaded her from doing that. She is now set to graduate next year and wants to start her own event management business.

The former students both said Dr Koo had been not just a lecturer but also a mentor. Mr Teo said Dr Koo had guided him when he had "all the rage in me - rage against the world, against life".