More than 100 middle school students and teachers at the Maiji Junior Middle School in the city of Tianshui remain trapped Thursday afternoon, the official Xinhua news agency reported.
The school, which is in a mountainous area in the province of Gansu, was isolated when a rainstorm-triggered flood washed away the only bridge linking the school to the rest of the city.
Education officials said the school is a boarding facility with dormitories and cafeterias, which can supply the trapped people with enough food for two to three days.
Officials said floodwaters, which are starting to retreat, will not threaten the safety of those trapped.
The schools gate and some walls were destroyed in the storm that began Wednesday night.
The Lanzhou Central Meteorological Station issued a red alert for continuous rain in Gansu Thursday and said there is a high risk of more flash flooding and other disasters.