Twenty-five children in a school bus were let down badly from two flanks on Wednesday. First, by alleged bandh supporters who threatened to burn the vehicle and then by a government that had ordered schools to stay open but could not ensure the safety of the students of an institution that heeded its call.

The school bus was stopped in the morning not too far from the airport by a group that broke its windshield as the children cowered inside.

Three teachers got off the bus and pleaded with the attackers with folded hands to be allowed to go. The mob let the driver turn back after 15 minutes, an FIR filed by the principal at Airport police station said.

“Bus Route number 1 vehicle number WB19H8304 of Delhi Public School Megacity, Kolkata having students and teachers on board coming to school was held up and attacked by an angry mob with bamboos. The mob was agitated and threatened to BURN the Bus and kept hitting the body of the bus and window panes,” the FIR said.

The incident took place around 7.10am when the bus, carrying students of Classes IV to XII, was on its way to Delhi Public School Megacity.

“The windscreen of the bus was cracked. With pleaded request from the teachers and desperate cries from the students, they finally let the bus go after 15 minutes of extreme harassment. They repeatedly questioned the school staff regarding the school being open and kept repeating threats of BURNING the Bus even as it drove off,” the FIR, filed by principal Indrani Sanyal, added.

“A case has been started and we are looking for the people who stopped the bus and smashed its windshield,” Gyanwant Singh, commissioner, Bidhannagar Commissionerate, said.

BJP national secretary Rahul Sinha said of the attack on the school bus: “I don’t believe BJP workers have done that. This is a conspiracy by Trinamul and needs a proper investigation. But whatever happened is unfortunate and uncalled for.”

Sanyal said the children were traumatised and the teachers had to calm them down. “The teachers and students were brave enough to face the situation and lucky enough to come out of it. But schoolchildren and emergency services like ambulances should never be targeted under any circumstances, irrespective of political affiliations. We had kept the school open adhering to the government directive,” the principal said.

Education minister Partha Chatterjee had on Tuesday appealed to all private schools to remain open on Wednesday and warned of action if they stayed shut.

Officials said the bus was headed for school as in any other day when the driver noticed around 25 people blocking the road in front of BT College in Birati.

The teachers later told school officials the crowd kept asking why the school had been kept open, with some screaming “the bus should be burned down”. Three of the teachers, one of them a woman, got off and requested them to let the bus pass because it carried schoolchildren.

The mob eventually let the driver make a U-turn after asking him to drop the children back home, said Anurag Agarwal, the owner of the bus.

The bus took the children to school by another route after the teachers had called the authorities. The bus picked up some others before it reached the school around 9am, half an hour late. Police escorted the bus when it dropped the children back home after school got over in the afternoon.

Driver Rabindra Prasad Mahato drove the bus to Airport police station after dropping the students at school. “An officer took pictures of the cracked portion of the front glass and took down my name and address along with other details. The same officer was present in the afternoon while the police escorted the bus out of school,” Mahato said.

Agarwal, owner of Urban Parivahan Services Private Limited, which runs the bus service, said the company had 90 buses that ferried students of all DPS schools in the city.

“When we checked the CCTVs installed in the bus, we saw some of the children crying. The bus damaged on Wednesday is barely a year old,” he added.