After dinner, under the flagpole of the school playground, Wan Yongkang connects a newly purchased microphone to the stereo and his mobile phone, and calls on several students to sing together. Behind him, a line of six students, hands outstretched and clutching the shoulder of the person in front, walk toward the shower room. Those who just suffer from amblyopia - commonly known as "lazy eye" - lead the train of students. The sky gradually darkens, but this does not affect them in the pursuit of their activities.

Not far away, a melodious erhu tune comes from the dark classroom. The schoolteacher Shi Pengqiang is leaning against the classroom wall, holding the erhu, a two-stringed bow musical instrument, and several students sit in their seats. Not to be disturbed by the karaoke under the flagpole, the windows of the classroom are shut. They don't turn on the light, the music lesson in progress just takes place in the dark.