The bus, carrying pupils from Hungary, collided with a roadside column as it exited the A4 motorway near Verona late on Friday, the BBC reports.
Italy’s national fire service said that another 39 people had been injured.
The bus was returning to Budapest from France, where the pupils had been on a mountain holiday.
Italian news agency Ansa said a number of the pupils, who were mainly boys aged between 14 and 18, were thrown out of the vehicle when it collided with the pylon.
It is not known why the bus left the road.
Others were trapped inside the bus when it caught fire, Ansa said. Ten of those in hospital are seriously hurt, it said.
Ansa quoted Judit Timaffy, Hungary’s consul-general in Milan, as saying a number of the pupils were saved by a sports teacher, who returned to the middle of the fire to drag them out. The teacher suffered burns as a result, she said.
The death toll is not expected to increase, the fire service added.