Detention

Detention is a 2019 Taiwanese supernatural psychological horror film directed by John Hsu and based on the popular horror video game of same name developed by Red Candle Games. Set in 1962 during Taiwan's White Terror period, two students are trapped at their hillside high school at night. While trying to escape and find their missing teacher, they encounter ghosts and the dark truth of their fate.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.

Poster © the film's rights holders.