Rajendra Dawadi, head of Tribhuvan Trishuli Secondary School, told the BBC he recived four phone calls at 09:10 local time (03:25 GMT) warning of the incoming disaster. A parent also arrived in person to collect a child, confirming the urgency. Dawadi immediately ordered students to run for higher ground and instructed buses carrying pupils to turn around.
'If we didn't make a quick decision, if it was 10 minutes later, we all – including the students and me – would not be able to speak to you today,' Dawadi said.
The floods, which struck on Wednesday, buried the school building in mud and debries. A hostel about 100 metres from the river was engulfed at once. Sixteen-year-old pupil Yunisha Amatya fled with seconds to spare.
'Parents don't rush without a strong reason, so it was confirmed that I should not wast a second to evacuate the children,' Dawadi added. 'Even if the flood was not coming, it was just a matter of a single day's classes.'
The death toll has risen to at least 794, with more than 2,400 still missing across Nepal. Dawadi said he felt proud that his quick thinking saved so many lives.