Ornge initially said about 12 children were seriously injured in a crash involving a school bus and a minivan.
Deputy Chief J.C. Gilbert said all those transported were taken to Collingwood General and Marine Hospital to be treated for their various injuries.
"Our vehicle was travelling southbound when a northbound vehicle containing about seven or eight passengers crossed over and hit the front of our motor coach, severely impacting that vehicle and the motor coach as well", said Glenn Attridge.
A bus arrived on scene to shuttle students to the local arena where they were given food and drinks until another coach came to pick them up around 4:30 p.m., Sewell said.
Ornge said it airlifted five of the injured to Sick Kids, one to St. Michael's and one to Sunnybrook hospitals in Toronto. The ages of the two adults were not available, and Leon said the van had a USA licence plate.
Shewell said all eight people in the van are in "serious, life-threatening" condition.
Leon said the children and adults on the bus suffered minor cuts and bruises and the driver was likely shaken up by the crash.
Clearview Fire Department Chief Colin Shewell said 41 teens, three adult chaperones and a driver were on the bus. They are being taken to the Clearview Community Centre.
They were returning to a Hamilton high school after a day at Blue Mountain.
He added that the driver was "pretty shook up" after the crash.
Police continue to investigate the cause of the crash.
Highway 26, which was closed for hours after the head-on crash, has been reopened.