A 15-year-old boy has been stabbed at his school, police said.
The teenager was wounded in the leg in an incident in the lobby at Southfields Academy in Wandsworth, south-west London, Scotland Yard said.
A police spokesman said the boy's injury was "not serious" and that three people had been arrested on suspicion of GBH.
A Metropolitan Police spokeswoman said: "Police were called at approximately 3.10pm on Tuesday November 10 to reports of a male, believed aged 15, suffering a stab injury to the leg after an incident in the lobby area of a secondary school in Merton Road, SW18.
"London Ambulance Service attended and the male was treated - his injury is not serious. Three people have been arrested on suspicion of GBH and remain in custody."
London Ambulance Service said the boy had been taken to a south London hospital for treatment.
A statement was posted on the school's website this afternoon, signed by principal Jackie Valin and headteacher Wanda Golinska.
It read: "As some of you may be aware already, an incident occurred outside the school earlier today. The student involved is in a stable condition.
"If you or your child have any information about this incident then please telephone 101 and ask for Wandsworth CID."