"The accident has left some 16 dead. Thirty injured people have been evacuated," Ruben Alva Ochoa, the governor of the Huanuco region, told RPP radio.
The accident occurred on Sunday as the school children, teachers and parents were returning home on the truck from a school event celebrating Peru's flag day.
Alva blamed poor road conditions and a miscalculation by the truck's driver, who backed up off a 100 meter (300 foot) high cliff.
In the first half of 2014, 1,406 people were killed in road accidents, according to official statistics. The death toll in 2013 was 3,590 people.
