Alvin Zhao, nine, was found wandering the streets of Macquarie after his school bus to Higgins crashed on Monday afternoon.

Father Joseph Zhao said it was only the second time his son had caught the bus back from Brindabella Christian College and with no mobile phone he had little idea of how to get home.

"The bus driver apparently asked all the students to walk home by themselves," he said.

"That point is five kilometres from home. And he has never been that way before.

"We didn't know what had happened to him."

Worried sick about their missing son, Alvin's parents then received a phone call from an unknown number.

"A young voice asked if I am Alvin's father," Mr Zhao said.

"The young man told me that their school bus had broken down close to Macquarie Primary School.

"He had noticed Alvin and he called me immediately."

The boy was Jordan King, a 15-year-old student at Emmaus Christian College in Dickson.

"When I saw Alvin on his own I thought to myself, 'Where could he be going'," Jordan said.

"I was hoping that his house wouldn't be that far away. But I thought I'd check.

"When he said his house was in Higgins, I knew he wasn't going to be able to walk all the way back there."

Mr Zhao said he could not thank Jordan enough for taking the time to keep an eye out for his son.

"He was very thoughtful and very nice. He was not even from the same school.

"We have been really touched by the young man's actions. I think the whole of Canberra could learn a thing or two from him.

"He's a local hero in our eyes."

Jordan's mother Rowena said she was immensely proud of her son.

"I was very proud of Jordan when he told me what had happened," she said.

"He has always been very good with younger children."

Both Mr Zhao and Mrs King questioned why the driver allowed the young passengers to wander away from the bus on their own.

Rather than leaving the stranded passengers to fend for themselves, they should have made an attempt to phone the childrens' parents, Mr Zhao said.

"I wouldn't want my year four walking home like that," Mrs King added.

A spokesman for Transport Canberra and City Services said the department would be investigating the incident concerning Alvin.

"The students on the bus at the time were allowed to disembark due to the incident causing a total power failure resulting in no air-conditioning or circulation," he said.

"ACTION operations immediately organised for a replacement bus and for transport officers to attend which is normal practice during these situations.

"Some students chose to have their parents pick them up from the location whilst some others that lived close by, chose to walk home.

"The safety of students is of the highest priority for ACTION."