The Year 12 student was rushed to hospital in a life-threatening condition after being found injured in Prince Imperial Road around 4.20pm on January 6.
His condition has since been assessed as stable, according to police, but he remains in hospital.
His injuries are non-life threatening and non-life changing.
The college remains closed today while police investigate the circumstances surrounding the attack.
Two teenagers, a 19-year-old man and a 17-year-old girl, have been arrested on suspicion of attempted murder and conspiracy to commit murder.
Both remain in police custody.
Detectives are appealing for information from the public.
Anyone who can assist the investigation is asked to call 101 or contact @MetCC on social media, quoting reference CAD 4354/6Jan.
Alternatively, information can be provided anonymously to Crimestoppers at 0800 555 111.
A spokesperson for Metropolitan Police said: “A 19-year old man and 17 year-old girl have been arrested on suspicion of attempted murder and conspiracy to commit murder on Tuesday, 7 January following the stabbing of an 18 year-old man at Prince Imperial Road SE18.
“The victim is in stable condition and remains in hospital with non-life threatening and non-life changing injuries.
“Both suspects remain in police custody.
“The investigation is ongoing.
“Anyone with information is asked to call 101 or ‘X’ @MetCC and quote CAD 4354/6Jan.
“You can also provide information anonymously to the independent charity Crimestoppers on 0800 555 111.”
