Not One Less (1999) on Netflix

In a remote mountain village, the teacher must leave for a month, and the mayor can find only a 13-year old girl, Wei Minzhi, to substitute. The teacher leaves one stick of chalk for each day and promises her an extra 10 yuan if there's not one less student when he returns. Within days, poverty forces the class troublemaker, Zhang Huike, to leave for the city to work. Minzhi, possessed of a stubborn streak, determines to bring him back. She enlists the 26 remaining pupils in earning money for her trip. She hitches to Jiangjiakou City and begins her search. The boy, meanwhile, is there, lost and begging for food. Minzhi's stubbornness may be Huike and the village school's salvation.