The youth, who cannot be named for legal reasons, pleaded guilty to violent disorder and possessing an offensive weapon following an incident in Dudden Hill, north-west London, on May 30.
Jamal Ringrose, 15, was treated for stab wounds at the scene but died in hospital five days later.
A different 16-year-old boy has been charged with Jamal’s murder.
Police were called to reports of a stabbing and disorder at around 10.36pm and paramedics treated Jamal for stab wounds before taking him to hospital.
Despite the efforts of doctors and nurses, he died on June 4.
At Bromley Magistrates’ Court, the 17-year-old entered guilty pleas to both offences and was remanded in youth detention accommodation ahead of sentencing.
Court records state he was remanded after conviction because of concerns including his previous record, breaches of bail and the seriousness of the case.
The record also states: “The offence is serious where another young person has lost his life.”
He is due to appear at Bromley Magistrates’ Court in December for sentencing.
Following Jamal’s death, officers were continuing to pursue several lines of enquiry, police confirmed.
Jamal’s mum, Whitney Ringrose, told London Now her son was a “big foodie” with a passion for music.
She said: “Jamal is honestly the light of my world. He is the best thing that has ever happened to me, a true blessing from God.
“Jamal always, since he was young, has had me in fits of laughter. He is a very bubbly character and very unique with a capital ‘U.’
“Jamal had the most beautiful smile and the warmest, welcoming eyes – the most beautiful brown eyes. He was taken way too soon.”
But behind her son’s “bubbly” nature Whitney claims he had his own struggles, falling in with the wrong “company” and being connected to “drugs” whilst growing up in Brent.
She said: “He is Special Education Needs, he has ADHD, so how he views the world is slightly different. He would struggle with things like social cues and things like reading the room.
“It was only as he got a little bit older that he was able to actually take into consideration how people actually are.
“When he was younger, like Year 6, early high school, those kinds of ages, he was very very susceptible to the assumption that everybody is his friend. He was extremely vulnerable.
“All children are vulnerable but there was an additional layer of vulnerability with him because of his additional needs.”
