Neighbours fear a school will be left with “blood on its hands” if plans to build a new access route to its playing fields are approved.
University College School has applied to move the entrance of its sports ground, in Ranulph Road, Cricklewood, to the sharp bend where Hocroft Road and Farm Avenue meet.
But residents have rallied together to block the proposals, which they say will cause hazardous traffic jams and inevitable accidents on the picturesque street.
Sidney Myers, of Hocroft Road, said: “It is a notoriously dangerous road and people never drive safely down it.
“It is irresponsible for a school to consider endangering children in this way - it is an extraordinary situation. The school will have blood on its hands if there is an accident.
“It will be chaos.”
Back in 1999, Barnet Borough Council rejected the same proposal, saying it would make the already dangerous road less safe.
Many voiced objections at a consultation event last September - so former students were shocked to receive a newsletter which said there had been a “positive” response.
Former head boy Andrew Barnett, who has lived in Farm Avenue since 1961, said: “I am disappointed in my old school for their complete intransigence.
“I am concerned about the security, safety and aesthetics of this. They school just see it as something they want to do - they don’t care.”
The £5,720-a-year school, in Frognal, Hampstead, also plans to knock down the old pavilion and replace it with a new building.
The £6million plans include a 25-space new car park, but residents feel it will become a “hiding place” for burglars in an area which is already high in crime.
Many believe the car park will not be used by parents, who will instead park on the streets or in front of driveways when making quick drop-offs or pick ups.
Wendy Bond spent almost two hours monitoring the traffic on fireworks night in November - and said it was a “chaotic sign of things to come”.
She said: “They should listen to us - it could save someone’s life.”
Retired solicitor Graham Barber, of Farm Avenue, said: “We believe they are going to turn a dangerous bend into a death trap.
“Parents take no notice of the rules and just park where they want at the moment, but this is going to make things so much worse.”
In a statement, UCS said it hoped the new access route would help improve its facilities, security and traffic arrangements.
It said: “We have sought planning permission to build a new sports pavilion to better serve our pupils, parents and visitors and create a far safer vehicular entrance at Farm Avenue.
“Currently the local roads can be burdened with traffic for collection and parking. By providing on-site parking for coaches and cars we hope to ease pressure on surrounding streets.
“Our architects are working with traffic engineers to ensure access to the site is safe and secure, since ensuring the safety of both visitors and local residents is paramount to UCS.”
The plans will be heard at Barnet Borough Council's planning committee on March 6.