According to the school, the teacher has admitted to the abuse, saying: "I wanted to shake him up, but I went about it the wrong way."
"Don't joke around, kid! Do you understand? You're stupid," the teacher is heard yelling in the video as he repeatedly slaps the student's face, according to Agence France-Presse.
The assistant principal of Hamamatsu Nittai Senior High School told the AFP the teacher had also beaten another student on the same day.