Boy severely injured, classmate held in fight at SF school

A Sacred Heart Cathedral Preparatory sign hangs on the outside wall of the school building on Friday, May 16, 2014 in San Francisco, Calif. A Sacred Heart Cathedral Preparatory sign hangs on the outside wall of the school building on Friday, May 16, 2014 in San Francisco, Calif. Photo: Beck Diefenbach, Special To The Chronicle Photo: Beck Diefenbach, Special To The Chronicle Image 1 of / 1 Caption Close Boy severely injured, classmate held in fight at SF school 1 / 1 Back to Gallery

A 16-year-old San Francisco high school student was hospitalized with a life-threatening head injury and a classmate and fellow football player at Sacred Heart Cathedral Preparatory was arrested on suspicion of battery after a punch was thrown at a late-night party last week in Stern Grove, authorities said.

The altercation occurred late Oct. 29 in the wooded park near Sloat Boulevard and 19th Avenue and involved students and football players from Sacred Heart, authorities said. Police and school officials were providing little information about the incident between the two boys, both 16, who were not identified because of their age.

Sacred Heart’s director of athletics, Phil Freed, confirmed Friday that one student had been injured, one had been arrested and that “about a dozen” members of the football team had been suspended for the final game of the season Thursday night at Kezar Stadium, a loss.

The injured student “walked into a local hospital” early Sunday morning with “life-threatening injuries,” said San Francisco police spokeswoman Grace Gatpandan. The boy who allegedly caused the injuries later turned himself in, she said, and was booked with juvenile authorities on suspicion of battery involving serious bodily injury.

Because of the suspensions, Sacred Heart was able to field only about half of its 30-player football team for its game Thursday against Valley Christian High of San Jose, Freed said. Sacred Heart’s principal, Gary Cannon, declined to comment Friday, saying the “issues were an internal matter.”

A source close to the school, who asked not to be identified, said the injured student was believed to be getting better but that recovery “will be a long process.” He said Sacred Heart students were advised to stay out of Stern Grove, known to be a nighttime gathering and drinking spot for teenagers.

Steve Rubenstein is a San Francisco Chronicle staff writer. Email: srubenstein@sfchronicle.com