A star pupil with "a very bright future" has been stabbed to death in an unprovoked attack by a bandana and hoodie-clad gang.
Ajmol Alom, 16, was murdered in Spey Street, Poplar, east London, at around 9.50pm on Monday, and a friend of the same age was left with injuries to his face.
Detective Chief Inspector Andy Chalmers said Ajmol was with a "peaceful" group of fellow Bengalis when he was attacked.
Speaking at the scene, he said: "Initial indications are that Ajmol was with four friends. They were peaceful, they were conducting conversations at the location, Spey Street, which is behind me. They were then confronted by five to six other males who were wearing bandanas and were hooded. There appears to have been an unprovoked attack when the victim received his facial injuries and then Ajmol was stabbed."
Chris Dunne, headteacher at Langdon Park School, said Ajmol was a star pupil awaiting his GCSE results and had a "very bright academic future ahead of him".
"He was a very, very splendid young man," he said. "Hard working, industrious, but also a very caring and thoughtful young man. He was very able in all areas, but that didn't mean he didn't work incredibly hard. He came to all the revision classes, he worked flat out. The exam results will come out next Thursday and he will have very good results."
A 19-year-old man was arrested on suspicion of murder and is being questioned by detectives.
A man who said Ajmol's father was his cousin said he believed the teenager was predicted to get an A* in his maths GCSE. The man, who did not want to be named, said Ajmol lived on the Teviot Estate, where the attack took place, with his parents, two brothers and one sister.
Mr Dunne added that Ajmol was planning to take A-levels before going on to a "very good university" where he had spoken of studying medicine. He said the teenager had recently taken part in a conflict resolution project with other young people from Northern Ireland, in which he was "hugely active".
The boy's family are "completely devastated", he said.