The teenager was attacked at All Saints Catholic High School in an incident at 12.17pm on Monday.
A 15-year-old boy has been arrested on suspicion of murder.
At a press conference on Monday afternoon, South Yorkshire Police’s Assistant Chief Constable Lindsey Butterfield said: “It is with great sadness that I share with you today that a teenager has died following a stabbing… Our thoughts are with the boy’s family, his friends and the whole school community.”
She added: “We know that what has happened will cause significant distress and concern.”
Police would remain on the scene and in the local area to offer reassurance, she said.
ACC Butterfield declined to answer questions about whether the arrested boy was previously known to police or reports that the school had been locked down days earlier because of another incident.
She called on people to avoid speculating about what had happened. its most recent inspection by Ofsted in 2023.
According to its website its “mission is to fully prepare our students for the wider world and to send them into it equipped for life and for the service of others”.
The website adds: “We come together from diverse backgrounds, united by Christ, by the highest aspirations and by a thirst for excellence to instil in our students a respect for themselves, for others and for their environment. We take our inspiration for Jesus’ commandment to ‘love one another’.”
