Gunmen hijacked a school bus in the early hours of Thursday in Akure, the capital city of Ondo state, south-west Nigeria.
The incident occurred around 06:45 local time (05:45 GMT) while the driver and one of the school assistants were going round to pick up pupils.
The attackers, thought to be about eight in all, were traveling on motorcycles and were armed with guns, cutlasses and other weapons.
They forced the driver to stop and dragged him down from the vehicle threatening to kill him.
No student was kidnapped but the school assistant was driven off in the hijacked vehicle and was later released in a forest.
She told the BBC that she had to make her way back to a major road where she was given money for a fare back to Akure.
The school principal also confirmed to the BBC that none of the school pupils were taken away by the gunmen.
Nigeria has been hit by a wave of school kidnappings in recent months. In the latest incident 136 students were kidnapped from a school in Niger state by gunmen on Sunday.