"The disaster happened so suddenly, I am struggling to come to terms with it", the school's principal said.
Japanese soldiers rescued people by boat in Hiroshima, while others were rescued from rooftops by helicopters.
The death toll from torrential rains in western Japan reached 88 late Sunday, with over 50 others still missing after massive flooding and landslides destroyed homes and displaced tens of thousands.
Local government officials said pumping trucks were being deployed to help restore access to some of the worst-hit areas in the area, and with the rains stopped, water was starting to recede. Almost 50,000 members of the military, police and firefighting services were taking part in searches for people trapped, wounded or dead as a result of the floods, reported the Japan Times.
The western Hiroshima prefecture was hit the hardest by landslides, which claimed 37 lives, while 21 people died in Ehime, NHK reported. "If it were her, I wouldn't be able to stop crying".
An emergency management centre has been set up at the Prime Minister's office to handle the situation and some 54,000 military, police and fire department personnel have been dispatched to the flooded areas.
Intense rainfall triggered huge landslides and flash floods in Hiroshima, Okayama, Kyoto and other regions, while hampering rescue operations with dozens of people reportedly missing.
On Saturday morning, the Japan Meteorological Agency lifted special rain warnings issued the previous day for Hiroshima and Tottori prefectures in the Chugoku region and Fukuoka, Saga and Nagasaki prefectures in the Kyushu region.
Although a weather front had settled between western and eastern Japan, there was a risk heavy rains would continue as warm air flowed towards the front, it added, with already-saturated areas facing more rain on Sunday.
Major manufacturers in the area around Hiroshima and Okayama, such as Panasonic, Mazda, and Mitsubishi Heavy Industries, have shuttered factories.
Houses are partly submerged in water after heavy rainfall hammered southern Japan.
MIHARA (Japan) • Mr Masanori Hiramoto stood before his traditional home in the Japanese town of Mihara, speechless at the destruction caused by record rain that have killed dozens of people.
"I've lived here for 40 years. I've never seen this before", the 69-year-old oyster farmer told AFP.
Officials said 170 patients and staff had been evacuated from the hospital, while the public broadcaster NHK later said about 80 people were still stranded.
Nearly 2 million people were still subject to evacuation orders, while tens of thousands of rescue workers battled mud, water and rubble to search for survivors stranded in their homes.
But the project is ongoing, and many remain in harm's way.