It follows the incident in Prince Imperial Way at around 4.20pm yesterday (January 6).
Officers from the Metropolitan Police were dispatched to the scene where an 18-year-old male was found suffering stab wounds.
He has been taken to hospital with life-threatening injuries.
The entrance to the road from Red Lion Lane has been cordoned off, with a crime scene stretching over a green and across pavements in front of homes.
Medical kits can be seen strewn across the pavement.
The incident has forced the temporary closure of Shooters Hill Sixth Form College, which lies a short distance from the scene of the stabbing.
Pupils have been warned to stay at home in the wake of the stabbing.
Geoff Osborne, the college’s headteacher, has confirmed that the victim is a student in their year 12 key stage.
He said: “At approximately 4.20pm offsite in Prince Imperial Road yesterday a young man who is in Year 12 at Shooters Hill Sixth Form College was stabbed.
RELATED: Year 12 pupil stabbed near Shooters Hill College as students told to ‘stay at home’
“This incident continues to be investigated by the Police and we are not in a position to release more details other than that the young man is receiving medical care for his injuries.
“The college is offering support and counselling to anyone who has been affected by the incident.
“Our thoughts are with the family and the victim and we ask that everyone respects their privacy at this difficult time.”