A disciplinary teacher discovered that her 16-year-old student was a rape victim after confiscating the girl's mobile phone, Guang Ming Daily reported.
The teacher took the girl's handphone after the student was caught using it in class on Sept 29.
She was shocked to find indecent photos of the girl on the phone. The teacher informed the student's mother, who then confronted the girl.
She told them that she had sex several times with her 24-year-old boyfriend, whom she got to know through a mobile app a year ago.
The girl was sent to a hospital for a check-up and a police report has been lodged.