Hundreds of Nepali schoolchildren were saved by their teacher shortly before the school was inundated in last week's devastating floods. A Trishuli local, Surinder, said the floods "swept away the entire building"."Here used to be a three-storey school building in front of a temple and there was a market nearby," Surinder said."When floods hit this area, the teacher evacuated all the students and saved their lives."Surinder said Rajendra Dawadi, who is head teacher at Tribhuvan Trishuli Secondary School in Nuwakot, saved the lives of about 1,600 students.Houses sit partially submerged in Trishuli, in the Nuwakot district, where the Tribhuvan Trishuli Secondary School is located. (Reuters: Adnan Abidi)Mr Dawadi told the BBC he received calls warning of the incoming disaster."If we didn't make a quick decision, if it was 10 minutes later, we all, including the students and me, wouldn't be able to speak to you today," he told the BBC."A parent came and told me that 'a big flood was coming, I am here to take my daughter, I will take her'."Parents don't rush without a strong reason, so it was confirmed that I shouldn't waste a second to evacuate the children."I decided I shouldn't delay any more. Even if the flood was not coming, it was just a matter of a single day's classes."I feel proud that we saved so many lives."Mud covers a classroom at the Shree Bagheswori Madhyamik School, damaged in flash flooding. (AP: Niranjan Shrestha)Saved by a lunchbreakIn one of the areas worst hit by the floods, at another school, a group of schoolchildren managed to survive when they happened to leave their classroom for their lunchbreak.Children attending other classes at the Shree Bagheswori Madhyamik School in Galchhi also escaped because teachers told them to quickly evacuate their classrooms shortly before the waters came crashing in."The teachers said, 'There is a flood and you should leave bags and tiffins [lunch boxes]'," said Lakshmi Shrestha, the mother of a student attending the school."That's how they managed to survive."Shrestha was among mothers and children who began to return to their school on Sunday to find the kids' belongings and see what could be salvaged. The majority of the children at the school appeared to have survived the floods, the families said.A mother searches for her child's bag from a pile extracted from the mud. (AP: Niranjan Shrestha)Thick brown and grey mud coated the surfaces of school benches, walls and notebooks, while the school's courtyard was filled with sediment. Lines on the walls showed how high the water rapidly rose. A pile of small mud-caked backpacks, some with colourful key chains, were on the benches and floors, waiting to be claimed.A student smiles after locating her bag. (AP: Niranjan Shrestha)Kopila Mizar, the mother of a student, was unable to find her son's backpack, but remained positive."My son is alive, that is my biggest happiness," she said.At least 69 schools in Nepal's flood-devastated districts have been destroyed or damaged, putting education at risk for nearly 19,000 children, according to the non-profit Save the Children. Those numbers are likely to rise as rescue teams reach more areas, they said.Students' lunch boxes covered in mud. (AP: Niranjan Shrestha)The government ordered schools and universities to shut down for three days following torrential rains that triggered severe flash floods and landslides across parts of the country. University exams were also paused.With communities still receiving constant flood warnings advising them to move to higher, safer areas, it's unclear when classes will be able to resume.The disaster has killed at least 794 people and more than 2,500 people are unaccounted for in Nepal, according to the latest figures released by the Nepal police.Chinese authorities said 16 people were killed in Gyirong County, Tibet and 546 are missing.AP/Reuters