Editor's note: This series tells the stories of selfless individuals, from medical workers to volunteers, who are bravely fighting the virus outbreak with extraordinary dedication.

When the novel coronavirus hit China, schools throughout the country were closed and all classes went online.

But the students at Yanzijiao Primary School in Weishan Yi and Hui Autonomous County, which is located in the west of Yunnan province in Southwest China, have no luxury of online learning. They live in a mountainous area where communication signals are unstable.

The altitude difference in the area is also wide. The lowest elevation in the river valley is 1,146 meters, while the highest elevation in the region is 3,037 meters. Weishan county is 375 kilometers from Kunming, capital of Yunnan province.

But the 13 teachers of the school did not want their 265 students to idle their time away when staying home as part of social distancing measures.

"The students were supposed to return to school on Feb 24, but we told them to stay home to keep them safe (from COVID-19)," Bi Enquan, head of the school, said.

On March 16, the teachers returned to work and made preparations for the school's reopening on March 30. They disinfected the campus.

But the Yunnan provincial government asked the school to again delay the reopening because of a confirmed infection of COVID-19 at the seat of the county, which is 54 kilometers from the school.

As it was difficult to offer online lessons to their students, Bi decided to send all the teaching staff to the children's homes. The teachers gave new textbooks to every student, checked their homework and clarified their doubts about lessons.

It was a difficult mission for the teachers as the students live in 25 different villages.

"Some homes are so far away that two teachers drove three hours and walked 40 minutes to get there," Bi said.

Since it's a boarding school, students are usually picked up by their parents or relatives on Friday afternoon and brought back to the school on Sunday afternoon.

The teachers keep in touch with parents and guardians on WeChat groups.

"Nearly half of the students stay with their relatives, such as grandparents, as their parents are away working at other places," Bi said. "It's our duty to take good care of the kids."

When visiting the students' homes, some teachers carried their teaching tools with them, such as small blackboards. They taught them some Chinese characters, and how to solve math sums.

These "classrooms" could be anywhere outside, under the shade of trees or in the courtyards.

Two teachers, who are young mothers of infant babies, went to the students' homes with the babies on their back.

"Not a single teacher complained in the past month though he or she had to work harder than they usually do," Bi said.

Zhang Bin, 55, who teaches Chinese language for the fourth graders, said he had to take breaks often when walking the steep mountain road. "But I'm okay. We don't want the students to be left behind because of the coronavirus outbreak," he said.

"We're glad to hear the students are looking forward to returning to school after more than two months," Bi said.

There are 23 ethnic groups in the county, including the Han, Yi, Hui, Bai, Miao and Lisu.

On April 26, the fourth, fifth and sixth graders returned to school, while students from the first to third grades were back on Wednesday.