A mob of 30 schoolchildren violently turned on two police officers after they tried to search a suspect for a knife.
One officer was beaten to the ground and repeatedly kicked in the head, while his colleague was punched in the jaw when she tried to rescue him in New Cross, south-east London.
Several witnesses filmed the attack and police are appealing for anyone with mobile phone footage to come forward.
The officers were on patrol in Goodwood Road at 4pm on November 9 when they saw a teenager hiding a large knife and tried to search him, Scotland Yard said.
A group of up to 30 schoolchildren then turned on them.
Detective Sergeant Jenny White, of Lewisham police, said: “I’m appealing to anyone who witnessed this shocking attack on two officers to come forward and speak with us, particularly anyone with mobile phone footage of the incident.
“It happened at a very busy time of the day and there would have been a large number of people in the area.
“These officers go to work every day to keep the public safe and this demonstrates the dangers the police can face while carrying out these duties.”
A 15-year-old boy was arrested at the scene on suspicion of actual bodily harm and has been bailed until mid-December.
Anyone with information can call Lewisham police on 020 8284 8365 or Crimestoppers anonymously on 0800 555111.