All thanks to a Principal’s quick thinking, at least 1,643 students’ lives were saved.

On Wednesday morning, what began as an ordinary school day turned into a race for survival at Tribhuvan Trishuli Secondary School in Nepal’s Nuwakot district. When the morning bell rang, everyone thought it was a signal for class — only it wasn’t.

It was rather warning bell for everyone to run for their lives.

Within minutes, all 1,643 students were evacuated to higher ground as a devastating flash flood swept through the valley. The three-storey school building that was standing minutes ago, was now gone.

It was Principal Rajendra Dawadi, a 47-year-old English teacher who had only moments to take the call.

Initially, Dawadi believed the school was safe. The concrete structure stood about 60 metres above the river and was roughly level with a steel bridge linking the village to the eastern bank.

That assessment changed at around 9.20 am on Wednesday when a...