A 15-year-old boy has been charged with the murder of Jodie Chesney in east London, the Metropolitan Police said.
The teenager, who cannot be named due to his age, will appear at Barkingside Magistrates’ Court on Monday.
A second teenager, an 18-year-old man from Romford, is being held in police custody on suspicion of the 17-year-old’s murder, the force said.
He was one of four people arrested on Sunday as part of the probe into the teen’s death.
A 50-year-old man and 38-year-old woman, both from Dagenham, east London, and a 17-year-old boy, were held on suspicion of assisting an offender.
Jodie’s death sparked a national outcry over knife crime and detectives are continuing to investigate the stabbing on March 1.
The teen was playing music with friends near a children’s playground at Harold Hill, Romford, when she was knifed from behind in a seemingly motiveless attack.
She was pronounced dead just over an hour after officers were called at about 9.25pm.
A post-mortem examination gave the cause of the Girl Scout’s death as trauma and haemorrhage.
A 20-year-old man, Manuel Petrovic of Highfield Road, Romford, was later arrested and charged with her murder.
He is due to appear at the Old Bailey on Monday.
The Met has asked anyone with information about Jodie’s death to call Homicide and Major Crime Command’s Incident Room on 020 8345 3775.
They can also tweet @MetCC or call Crimestoppers anonymously on 0800 555 111.
This comes as the police launch Operation Sceptre in a bid to crackdown on violent crime.
On Monday, a week-long crackdown on knife crime begins across England and Wales in which surrender bins, stop-and-search and weapons sweeps will be employed to curb stabbings.
There have been 39 fatal knife attacks in Britain since the beginning of the year - with many of the victims and perpetrators being teenagers.
NHS data shows in the last five years the number of children aged 16 and under being treated for assault by a knife or other sharp objects rose by 93%, from 180 admissions in 2012-13 to 347 in 2017-18.