A 17-year-old boy has been arrested on suspicion of attempted murder after allegedly assaulting one adult with broken glass and injuring two others at a secondary school in Sheffield. South Yorkshire police said they had been called to Birley academy at 8.50am and had arrested the boy within minutes, while the school went into lockdown. Two adults suffered minor injuries and a child was also allegedly assaulted. All three had been checked over at the scene by paramedics from Yorkshire ambulance service, and the child had no visible injuries, the force said. “I know this will have been a frightening ordeal for all involved,” said Asst Ch Const Dan Thorpe of South Yorkshire police. “The two adults both suffered minor injuries, one from a sharp object that is believed to be broken glass. A child was assaulted and thankfully has no visible injuries. “I would like to praise the academy staff for the actions they took to help keep the school community safe. Birley is a close-knit community, and while these events concluded in a swift arrest, it will no doubt cause ongoing concern.” The officer said the 17-year-old boy remained in police custody, and that officers would remain at the school for reassurance in the coming days. The school’s headteacher, Victoria Hall, confirmed that the school would be open as usual on Thursday as she thanked students for their “exemplary behaviour”. “I’d also like to thank our staff, who prioritised the safety and wellbeing of all of our students,” she said. Pupils were sent home from the school at around 11am on Wednesday after the lockdown was lifted. A school spokesperson saidthis had been done “as a precaution” and that “this was not a decision taken lightly, but the safety of students and staff is paramount”. Outside the school, on the Birley housing estate on the south-eastern edge of Sheffield, parents said they had been shaken by the incident and were scared for the safety of their children. Sophie Jones told reporters she had received a text message from her daughter saying the school was “in lockdown, the lights had gone off, the doors were locked and she was hiding under her desk”. “It was really scary. I asked if she was joking because it seemed a really surreal situation. She has told me she was OK since then and I’m quite reassured that she is safe,” Jones added. Kath Grierson, who has a 15-year-old grandson at the school, said the incident would have been “so scary for the kids inside … They shouldn’t have to think about this kind of thing when they go to school. My daughter texted me to say the school was in lockdown, and I saw the news and thought, ‘Oh, my goodness.’ “I’ve seen this kind of thing on films in America, but you don’t expect it to happen here. But it just seems to be happening more and more. It’s very worrying.” Union leaders called for government action. Daniel Kebede, the general secretary of the UK’s biggest teaching union, the National Education Union, said: “The government needs to recognise the scale of the problem and adopt a public health approach to tackling youth violence, as did Scotland in the 90s. “This is another shocking incident happening on school premises. Violence has no place in our schools and colleges. Everyone in school – staff, students, teachers, and support staff – should feel and be safe. “Our thoughts are with the staff, pupils and parents at the Birley academy in Sheffield and with the people who were injured.” Patrick Roach, the general secretary of the NASUWT union, said: “This latest incident provides a further reminder of the need for robust action to be taken to keep our schools, pupils and teachers safe.”