Stevens fell to the floor, unconscious. He was taken to the Hospital of the University of Pennsylvania for treatment and is now recovering at home.
Jerry Jordan, president of the Philadelphia Federation of Teachers, said the attack on Stevens was "the worst injury" he has seen since a student punched Frank Burd in the face several times in 2007, causing him to fall and break his neck.
The student in Friday's assault was charged as a juvenile with aggravated assault and has been suspended pending expulsion.
Hill said it was not clear what prompted the exchange between Stevens and the student.
Superintendent William R. Hite Jr. said he was "very concerned" about these incidents and is working with Bartram's principal and city police to get to the heart of the situation.
"We have to continue to ensure that our staff members, and our students, are in a safe and supportive environment," Hite said.
Stevens was the third staffer to suffer injuries at Bartram last week. The school on South 67th Street in Southwest Philadelphia has struggled this year.
Its longtime principal left the district at the end of last school year, and a new principal lasted only a short time before being replaced. Like many district schools, Bartram also suffered the loss of a number of staffers due to budget cuts.
"The thing we noticed the most in terms of a difference from the year before was so many more students in the hallways" while class was going on, said Katie Clark Gray, who worked at Bartram last fall and for several previous years.
Gray, an artist with the Wilma Theater, worked with students on acting, writing, and improvisation skills. Because support staff had been cut, there were fewer staff members monitoring the halls and making sure students get to class, she said.
The teacher whose class Gray worked in covered up the window of his classroom door to dissuade hall walkers from knocking and disrupting class, she said.
Within a few months, there were three fights outside the classroom that had to be quelled, Gray said. "That was an unusually high number," she said.
The school was locked down in November when fights erupted in the cafeteria.
Jordan, the PFT president, said staffers told him during a recent visit that children roamed the halls during class time and interrupted classes. The school was so out of control that some students would smoke cigarettes and marijuana in school, and others would call takeout places for food, then stand at the front door during the school day to receive it, Jordan said.
He said the school's administration has not been willing to work with staff to address the problem.
"And when you don't have a lot of support personnel," he said, "you're asking for a lot of disorder."
Inquirer staff writer Martha Woodall contributed to this article.