What to know

• A 15-year-old former pupil killed one person and injured two others at a Polish school, police said, just a day after a 19-year-old wounded 10 people in an attack at another school.S1
• A 15-year-old former pupil killed one employee and injured two others at a Polish primary school on Thursday wearing a helmet-mounted camera, the second school stabbing in two days, possibly in response to an internet challenge, authorities said. A 37-year-old...S2