The boy was stabbed Tuesday, seconds after boarding the bus near the gates of Highbury Grove School, the London Evening Standard said. Police said the boy was attacked following a fight with another teenager.
The London Air Ambulance landed at the school and airlifted the teenager to a hospital, where he died Wednesday night, the Islington Tribune reported.
Police have arrested a 15-year-old boy on suspicion of attempted murder. Authorities said they were questioning him Wednesday.
The names of the victim and the attacker were not being released, but the Islington Tribune said both the victim and the suspect are thought to be from Hackney.
Police said it was the fifth stabbing of a teenager in the past three days, police said.