About a dozen children suffered "serious" injuries in the mishap, district officials said.
The mishap occurred when the driver lost control over the bus which was carrying the children from Taintigaon village to Brajsthali Vidyapeeth located on Sikandarpur road and landed in the pit, police said.
On getting the information about the incident, police, the school authorities and parents of the children rushed to the spot where locals had already gathered and started taking the injured to nearby hospitals, they said.
He said all the children were fine and undergoing treatment at different hospitals, adding the administration was taking care of them.