Brian John Riddell (54) pleaded guilty to careless driving causing injury following the August 22 incident.
His counsel, David McCaskill, said the defendant had felt the strain after the crash.
Seeing the children in a state of distress triggered the psychological hardship, Mr McCaskill told the Dunedin District Court yesterday.
Riddell was driving his Scania truck south along State Highway 1 between Palmerston and Waikouaiti, behind two school buses, at 3.25pm.
The lead bus prepared to pull over at Goodwood corner and the second slowed to the legally required 20kmh to pass it.
Its driver had activated its hazard lights, Judge Tony Couch said.
"You should have seen them slowing down."
Riddell tried to swerve to avoid a collision but it was too late.
Of the nine children aboard the bus, only a 15-year-old girl was injured.
She was sitting in the right rear of the vehicle and was thrown forward.
"As a result of the collision she received bruising to her right arm and received cuts on her back and legs," court documents noted.
Judge Couch called Riddell's actions "grossly careless" and noted he had a long history of poor driving.
Among other convictions, the defendant had been before the court three times for careless driving and 10 times for drink-driving.
What saved him from a heftier sentence was the fact the last traffic offence had been 13 years ago and the last act of carelessness two decades past.
"When you are driving a heavy vehicle, great care is required. As you know, they don't stop very quickly and if they collide with something they have potential to cause a great deal of damage," the judge said.
Riddell wanted to meet the victim to apologise but a restorative justice conference did not go ahead.
Judge Couch sentenced him to one and a-half months' community detention (a 7pm-7am curfew) at a Rolleston property.
He was banned from driving for eight months.
