Metal detectors and uniformed police officers carrying out pupil searches are set to become widespread across the capital's secondaries following the adoption of a new formal agreement by London's education chiefs.
School governors and local authority officers are currently signing up to the Metropolitan Police's Weapons in Schools protocol, The TES has learnt.
The deal means officers can screen thousands of pupils and target schools if they have intelligence information about children.
Previously, searches have been carried out on a one-off basis, but the first formal agreement of procedures between schools and police means many more will now take place.
If the new processes are judged successful, similar initiatives are likely to be rolled out nationwide.
Some observers have warned, however, that these might end up by criminalising children with an assumption of guilt. They are also worried about the blurring of authority in schools between teachers and the police.
The extent to which the changes will mean an end to teacher-led searches is not yet clear.
The introduction of the new protocol comes as a new initiative is set to see hundreds of thousands of children get a police escort home from lessons when patrols come into force across the country this year. This means that pupils will effectively be policed from morning to evening on every school day.
The Metropolitan Police says searches carried out through the new protocol are designed to be a "strong deterrent" for the minority who carry weapons to class.
"They are not about criminalising young people and very few weapons are detected," a spokeswoman said.
"Action in the event of weapons being found is taken on a case-by-case basis in discussion with the schools and colleges involved. They are used more to ensure that all young people are aware of the dangers of carrying and using knives and other lethal weapons."
And unions have largely welcomed the development as a way of relieving the burden on teachers.
Mary Bousted, general secretary of the Association of Teachers and Lecturers, said: "It puts teachers' own lives in danger, we don't want anyone to be accused of inappropriate touching and it has the risk of damaging the relationship between pupils and staff if they have to frisk them. For these three reasons we think they shouldn't get involved."
But some criminal justice experts have warned that the constant presence of officers in schools means pupils will be living in a "policed" state.
Will McMahon, policy director for the Centre for Crime and Justice Studies at King's College, London, said: "If pupils get used to having police in school, through Safer School Partnerships, and police on their way home, they are effectively being policed constantly."