Two teenage boys were hospitalised after being stabbed at a school in Alleyn Park, Dulwich on Thursday afternoon, Metropolitan police confirmed.
Police officers were called to Kingsdale Foundation school around 15:30pm after reports of a stabbing.
Two 15-year-old boys were discovered with knife wounds, and were taken to a south London hospital for treatment by emergency services.
One victim who was in a critical condition has now improved to a serious but stable condition, a Metropolitan police spokesman told BuzzFeed News on Monday morning.
In a statement released on the night of the incident the school's headteacher Steve Morrison said that one of the boys had been discharged from hospital following "treatment for a superficial injury".
Morrison also confirmed that a student who was excluded from the school is involved in the incident.
One teenager has been charged in connection with the incident, accused of attempted murder, grievous bodily harm, and possession of an offensive weapon.
He appeared at Camberwell magistrates' court on Saturday 21 November. The 15-year-old was refused bail and was remanded in custody, the Evening Standard reported.
The teenager will remain in custody until his next court appearance at Woolwich crown court on 18 December.