Ajmol Alom, 16, was killed in August last year when he and his friends were approached by four men in Spey Street, Poplar.
Alom was fatally stabbed in the thigh, and his friend Azime Rob, also 16, was stabbed in the face. Both teenagers were taken to an East London hospital where Alom later died.
Aminur Nadir Khan, 19 of Robin Hood Gardens, Mashudur Rahman, 22 of Victoria Street, and Ali Akbar Choudhury, 20 of John Smith Mews, were found guilty on two counts of murdering Alom, and grievous bodily harm with intent to murder Rob.
A fourth man Muhammod Malik, 22 of John Smith Mews, was found not guilty on all counts.
Alom, who was said to have “a very bright future” ahead of him, had been days away from receiving his GCSE results when the attack happened.
Detective Inspector Julie Willats said: “Ajmol was an innocent teenager enjoying a summer evening with his friend Azime and others when they were targeted in an unprovoked attack by a group of young men with knives.”
“Azim and Ajmol were both stabbed, the latter fatally. This incident highlights the misery that knife crime causes. I hope the verdict acts as a deterrent to those who carry or use knives or associate with others who do so.”
The trio will be sentenced at Snaresbrook Crown Court on Friday 2 May.