His son, who has autistic spectrum disorder, has always found it difficult to express himself.
Now, the 13-year-old boy also gets nightmares almost every other night after his science teacher forcefully pulled him out of the classroom on July 2 last year, his father said.
"My son was treated worse than a dog," the ice cream seller, 65, added.
The teacher, 36, was sentenced to 60 hours of community service in court yesterday after pleading guilty to one count of using criminal force on the boy who was then 11.
The teacher and father cannot be named to protect the boy's identity.
Deputy Public Prosecutor Dwayne Lum told the court that the boy also suffers from attention deficit hyperactivity disorder, "characterised by hyperactivity, inattentiveness and impulsivity".
On the morning of the incident, he was late for classes at his primary school in eastern Singapore as he was unwell.
His 50-year-old mother accompanied him to school at around 10.30am and left him outside his classroom. It was empty as the other children were then returning to class after assembly.
The teacher saw the boy standing outside the classroom when he and the other pupils got back.
When he asked the boy why he was late, the boy kept silent.
As a punishment, the boy was ordered to stand outside the classroom by himself.
The teacher became frustrated when the boy disobeyed him and entered the class. He grabbed his pupil's arms to force him out of the classroom.
Although the boy resisted, the teacher dragged him out to another classroom.
The boy's mother, who was waiting nearby, was alarmed when she saw the incident.
She immediately informed the vice-principal and made a police report that day.
During mitigation, the teacher's lawyer, Mr Chia Ti Lik told District Judge Christopher Goh that his client, who has eight years' experience as a teacher, was "operating under pressure and stress" at the time of the offence.
Mr Chia also said that the boy was known to have behavioural problems and was involved in at least two other incidents with teachers in the school last year. Court papers did not mention what they were.
The father told The New Paper that the youngster now sees a psychiatrist every month. The psychiatrist has told him that his son needs a full-time caregiver.
As a result, his wife had to stop helping him with his ice cream business to keep an eye on the boy, who is now in secondary school, and his 10-year-old brother.
HID IN CUPBOARD
"Now, in school, whenever my son recalls last year's ordeal, he will have a fit and want to go home," the father said.
"A few times, he even hid inside a cupboard. The teacher will then call either my wife or me and we have to go there and pick him up."
He said he and his wife used to sell ice cream from 9am to 11pm every day, with her taking the morning shift and him the afternoon.
Since the incident, he works alone for only about three hours every day.
"Previously, we could earn about $2,000 a month. Now, I take home only about $700."
For using criminal force on the boy, the teacher could have been jailed up to three months and fined up to $1,500.
Responding to queries by TNP, the Ministry of Education said that it takes a serious view of misconduct by teachers. Those who fail to comply with its standards of conduct will be subjected to disciplinary action.
A spokesman said that in this case, the teacher, who was appointed in March 2005, was interdicted (a technical term for suspended) from service. The e-mail reply did not specify the period of suspension.
This article was first published on November 21, 2014. Get The New Paper for more stories.