The 69-year-old male driver of the bus that crashed near Inglewood today has died, police say.
The crash happened at 3.30pm, and police said the bus was 'Route 3022'.
They said the bus had gone off the road and rolled down a bank into a ditch.
There were 13 passengers aged 12 to 17 on the bus at the time of the crash.
A St John spokesperson said the passengers had minor injuries.
Police said 10 passengers had been taken to Taranaki Base Hospital, and three others were assessed and had now been released to their parents.
They said 12 students had now been discharged, while one remained in hospital in a stable condition.
Six ambulances and an intensive care paramedic attended the scene.
The Serious Crash Unit would investigate, and State Highway 3 remains closed near the intersection with King Road.
The principal of Inglewood High School said it was too early to say what caused the crash.
Rosey Mabin said none of the 13 students had been seriously injured.
"Our local community has been wonderful in its support and we're really grateful for their respectful response."
Police were ferrying students back to Inglewood High School and advised parents to meet their children there.
On its Facebook page, the school said the Egmont Village Bus had been involved in an accident.
"This is a developing scenario but as far as we are aware, no one has been injured. We have been told that the police will be ferrying students back to Inglewood High School. This is all we know at present. We will keep you updated."
It asked parents to refrain from coming down to the school.
Traffic is being diverted at the intersection of SH3 and Lepper Road, and police are warning motorists there could be delays in the area.
Tranzit has confirmed it was one of its buses involved in a crash.
Its managing director, Paul Snelgrove, said he had very little information about what happened in the crash, but the company's Taranaki area manager was at Inglewood High School being briefed by police.
All Tranzit's buses were tracked and that alerted the company, he said, when the Inglewood school bus came to a stop this afternoon.
Mr Snelgrove could not confirm what make of bus was involved in the crash, or whether it was carrying only college pupils.
SH3 INGLEWOOD - SERIOUS CRASH - 3:55PM— NZTA Central Nth Is (@NZTACNI) August 8, 2018
Due to a #crash, this road is CLOSED near the intersection with King Road. Please follow the directions of emergency services on site, and avoid the area if possible. ^HJ pic.twitter.com/iD49RW0Xdh