The suspect, who was arrested over the weekend, was set to appear in custody at Bromley Magistrates’ Court on Tuesday.
Two girls, aged 16 and 17, were found suffering from stab injuries by officers and an ambulance crew.
The victims, who were known to each other, were rushed to hospital after an air ambulance landed in the grounds of a nearby B&Q.
The 16-year-old was treated for life-threatening injuries but officers have now said her condition is “serious but stable.”
The second girl’s wounds are not life threatening.
Three other boys, all aged between 16 and 17, were also arrested on suspicion of attempted murder.
But two have been released on bail and the third has been released with no further action.
Detective Sergeant Rob Merrett of the Central South Command Unit, said: “Our investigation is still ongoing and I continue to urge anyone who has information, pictures and video that could assist us to make contact immediately.
“It is imperative that we work with the community to fully establish what has happened here and bring any offenders to justice.”
Watch the latest videos from Yahoo UK News