The headteacher of Langdon Park School has said that "out of all his students", Amjol Amol was the "least likely" to be involved in violence. Chris Dunne added that the teenager had been working in Northern Ireland to promote peace in local communities.
A post-mortem is due to take place tomorrow.
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Scotland Yard said the male youths will appear in custody at Westminster Magistrates' Court on Saturday.
The family of Oliver Dearlove urged people to "think again" before using their fists, as the man who killed him began a six-year jail term.
London Fire Brigade took Southwark Council to court on four charges in relation to safety breaches at Lakanal House in Camberwell.