The school bus driver thought the 11-year-old boy had fallen asleep in his seat.
But when he tried to wake the boy upon reaching Maris Stella Primary School yesterday morning, the Primary 5 pupil did not respond.
He was later pronounced dead at the KK Women's and Children's Hospital (KKH).
The New Paper understands the boy was on his way to school when he became unresponsive.
The Singapore Civil Defence Force (SCDF) received a call at about 6.55am yesterday and sent an ambulance to the school.
Police received a call around the same time yesterday asking for help "at 80, Bartley Road".
They found an 11-year-old boy unconscious when they arrived and he was taken to KKH, "where he was subsequently pronounced dead at about 8.46am," their spokesman said.
The family told media that the parents were in Singapore at the time of the incident.
An SMS that was circulated around Maris Stella Primary yesterday informed all of the incident and asked them to pray for the boy and his family.
One parent, who declined to be named, said the boy had a fever on Mondayand was sent home early.
He said: "The school principal spoke to his class and told them about the news. We heard he was an only child and his parents are currently out of the country."
Mrs Woo Soo Min, principal of Maris Stella Primary, said in an e-mail to TNP that the school was "saddened by the passing of one of our students".
"We are in touch with the family and are providing assistance and support to them during this difficult time. We are also providing emotional support to affected staff and students. As the police is investigating this case, we are unable to comment further," she said.
Police are investigating the unnatural death.
Correction note: An earlier version of this story said TNP understood that the boy's parents were overseas at the time of the incident. Family members have told media that the parents were in Singapore. The story has been corrected.
This article was first published on Aug 31, 2016. Get The New Paper for more stories.