A 15-year-old boy has been charged with the murder of Tamim Ian Habimana.
The teenager, who was arrested on Thursday, has also been charged with the attempted murder of another 15-year-old and possession of an offensive weapon.
A 14-year-old male and a 15-year-old-male, who were both arrested on suspicion of Tamim’s murder on Friday, remain in custody at a police station in south London.
Det Ch Insp Richard Leonard, the officer in charge of the investigation, said: "I hope this reassures both Tamim’s family and the wider community of our dedication to bringing justice for his murder."
Police have urged anyone with information about the killing to come forward.
Police were called at 5.23pm on Monday, July 5 to reports of a stabbing on Woolwich New Road, SE18.
Officers attended the scene and found Tamim, a student at Harris Academy Greenwich, suffering from a single stab wound.
Despite the efforts of emergency services, Tamim was pronounced dead at the scene at 6.08pm.
His next of kin are being supported by specialist officers, the force said.
In a joint statement to parents, Harris Academy Greenwich executive principal George McMillan and Principal Ben Keely said: “We are shocked and devastated at this tragic and senseless loss of a child’s life.
“Our thoughts and prayers are with the victim‘s family and we will do everything we can to support them at his time.
“We are also supporting students very closely, particularly those who knew him well or were in his year group.
“We also reiterated our frequent message about staying away from flashpoints in the area, which are Woolwich town centre and the local McDonald’s.
“We ask parents to help us reinforce the message that our children should go directly home after school each day.”
So far, 21 teenagers have been killed in London in 2021.