The bus, carrying pupils from Hungary, collided with a pylon as it exited a motorway near Verona late on Friday.
Italy’s national fire service said on Twitter 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.
The death toll is not expected to increase, the fire service added.
Hungarian media reported that the country’s consul in Milan has arrived in Verona.