68-year-old substitute English teacher, Pewu Johnson unconscious on the floor after being thrown to the ground by a student.An 18-year-old student at Bartram High School in Southwest Philadelphia may face criminal charges after knocking out a substitute English teacher.

The altercation began when a female student got up and sat on a male student’s lap. Substitute teacher Pewu Johnson, 68, told the pair that doing so was against the rules.

According to Philadelphia NBC affiliate WCAU, the male student told Johnson “Get the f–k out of my face.” Johnson then told the male to leave the classroom and threatened to go get the principal. While Johnson was walking out the door, the student allegedly grabbed him from behind and threw him to the ground with sufficient force to knock him out.

“The boy dropped me down with so much force,” Johnson told WCAU. “I was out.”

“No forms of violence, especially against teachers, should be tolerated,” Philadelphia Councilman Kenyatta Johnson told Philadelphia CBS affiliate KYW-TV. “So we want to make sure that teachers are safe, all young people are safe, and most importantly, that there’s a zero-tolerance policy toward any type of violence against any teachers.”