Knife crime and school exclusions are likely to be two symptoms of the same underlying problems, according to the head of Ofsted.
Amanda Spielman said there was a “harmful narrative” developing that exclusions must cause children to join gangs or carry knives.
But the chief of the inspections body added the issue was “too complex” to be reduced to binary arguments, and that schools cannot tackle the issue alone.
Ms Spielman said: “Schools can and should play their part, and many are.
“But this has to be as part of a broader coalition, with the support of local partners and the police.”
The government is coming under increased pressure to act following the latest spate of violence, with 17-year-olds Jodie Chesney and Yousef Makki stabbed to death in separate incidents in recent weeks.
On Monday, in an exclusive interview with ITV News, a family shared its raw account of life on Britain's streets.
Two young brothers from Liverpool spoke anonymously about carrying knives for their protection.
One of the siblings said he "feels safer" by carrying a knife "because if he's pulling out a blade then I'm pulling out a blade".
Their mum said she believed it was safer for her children to carry a knife so they can defend themselves.
In response to an Ofsted report on safeguarding children in London from knife crime, Ms Spielman warned that decisions to exclude pupils for bringing knives into London schools do not always take the best interests of that child into account.
She highlighted that some schools are not conducting knife searches, or teaching about knife crime, because they worry about how it will make them appear.
Ms Spielmam said: “Many school and college leaders we spoke to were trying to educate children about the dangers of knife crime and the risks of grooming and exploitation by gangs.
“However, some are concerned that if they do this they will be seen as a ‘problem school’, and subsequently avoided by parents.”
The report published on Tuesday states dialogue is missing between local safeguarding partners and schools about the purpose of searching, the impact on staff and pupils and evidence of the impact on knife-carrying.
“Additionally, some schools were wary of beginning to search children in case it sent the wrong message to parents – that suddenly their children were less safe – or because the school 100 yards away did not," it said.
The research is based on responses from more than 100 secondary schools, colleges and pupil referral units across the capital.
It comes after police chiefs linked rising knife crime to the exclusion and off-rolling of pupils.
Ms Spielman said: “There is evidence that points to a correlation between the two, but of course this does not prove causation.
“It seems just as likely that exclusions and knife crime are two symptoms of the same underlying problems, exacerbated by cuts to local authority children’s services.”
She added that schools and local authorities need to work together to improve education and other preventative work, to reduce the need for exclusions.
“Exclusions are a necessary and important sanction, but it is not acceptable, or legal, to exclude without due regard for the impact on and risks to the child being excluded,” said Ms Spielman.