What is the main story of the film No Child Left Behind directed by Zhang Yimou?

The story happened in a remote mountain village. There are such a group of children. Their life is very difficult, but it still doesn't affect their thirst for knowledge. There is also a teacher named Gao here. Although he hasn't been paid for several months, he still insists on being a rural teacher. Unfortunately, Miss Gao's mother was ill, so he had to take a month off to go home and take care of her.

So, the village head found a 13-year-old substitute teacher in the neighboring village. This man's name is Wei Minzhi. At the moment he saw Miss Wei, Miss Gao's heart was rejected, because in his eyes, she was just a child, but because of the harsh conditions here, no one wanted to come, so he had to promise the village head. Before he left, Mr. Gao repeatedly urged Wei Minzhi to take good care of the 26 students in his class. Before he came back, there was no shortage of them. Write a text on the blackboard every day for students to copy. Then she can sit at the door of the classroom and watch the students study by themselves. Every Monday morning, a flag-raising ceremony is held.

As a teacher, I am also very upset, because there is a naughty boy Zhang in the class. Because she is young, she doesn't regard him as a teacher. Wei Minzhi quarreled with him, and he was so angry that he overturned the table. There was not much chalk, so he spilled it all over the floor. A few days after this incident, Zhang disappeared and went to Zhang's home. When she got home and saw the boy's mother lying in bed, she realized that he had gone to work in the county with the villagers.

So, Wei Minzhi made a bold decision and went to the county to meet him. Xiao Wei led her classmates to move bricks in a nearby brick factory, earning 15 yuan, but it was still not enough to buy a ticket, so she had to ask her children to help her evade the ticket. Unexpectedly, the conductor found her halfway and got off the bus. She doesn't know how long it took, and finally came to the county seat. I finally found a TV station, and she went on TV. At the moment when she faced the camera, tears could not stop flowing down. After the program is broadcast, everyone helps to find someone. Finally, they found him, and soon they met. This story touched many people. The reporter returned to school with the sympathy of the citizens, and Wei Minzhi fulfilled his promise. No child was missing.