Emergency services were called to Llanfair Caereinion yesterday afternoon after the bus reportedly hit five children.
The Welsh Ambulance Service has said that three of the children were flown to hospital, while another was taken to hospital in a land ambulance. A fifth was discharged at the scene.
The driver of the bus was also taken to hospital by a land ambulance.
There has been no official word on the severity of injuries suffered by any of those injured in the incident, or which school the children attended.
The crash took place shortly before 3.26pm on School Lane, which approaches Llanfair Primary School. The location of the crash is just opposite Ysgol Uwchradd Caereinion High School – the town's secondary school.
Following the incident the bus could be seen hanging over the edge of a wall next to a tree where it had smashed through metal railings.
The bus has now been removed and council workers could be seen working on the railings this morning.
A spokesman for the Welsh Ambulance Service said: "We were called to an incident in Llanfair Caereinion on Monday afternoon at 3.26pm involving a vehicle and five children.
"Three of the five children were flown to hospital for treatment, while another child and an adult were taken to hospital by land ambulance. The remaining child was discharged at scene."
Powys County Council has said that support is being provided to both schools in the aftermath of the incident.
Dr Caroline Turner, chief executive of the council, said: “Our thoughts are with all those who were injured in yesterday’s incident and we wish them a speedy recovery.
“Officers from the council’s schools service are at both schools today to provide help and support to staff and pupils during this difficult time.
“The council will support any investigation into the incident by the appropriate authorities.”