The incident took place in Dailekh district, 550 km west of the capital Kathmandu, while children were appearing for a school-leaving examination, an army officer said.
''The injured are undergoing treatment in a local hospital,'' he said, adding the nature of the injuries was not known.
Dailekh is a stronghold of the Maoists who want to overthrow the Hindu monarchy and set up a single-party communist republic.
More than 13,000 people have died in the conflict since 1996 and according to a local child rights' group, about 400 of them were children.
There was no comment from the rebels about the attack.
REUTERS LR HS1424