Earlier this month, London Mayor Sadiq Khan and seven Police and Crime Commissioners wrote a letter to the Prime Minister warning that a “broken” school exclusion system is exacerbating the recent surge in violence.There has also been a sharp rise in the number of police-recorded knife crime offences since 2013, across every force area. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. Police officers in schools are to double in response to the knife crime epidemic, a senior Scotland Yard officer has revealed.Assistant Commissioner Mark Simmons said that the Met Police has made a “major investment” in hiring and training new officers to place in schools around London.The force now has around 420 officers in schools, up from around 280 a year to 18 months ago, he said, adding that a recruitment drive is now underway to get this number up to “just under 600”.“In the Met, we are investing heavily in more officers in schools,” Mr Simmons told the education select committee. “We need young people to see police officers not just as the person who stops them in the street and searches them – even though that may be an absolutely proportionate, legitimate thing for them to do – but someone who can become familiar to them, that can be approachable, that can engage with them day to day within the school. It’s a really important part of our approach and a major investment for us.”Mr Simmons was responding to a question about whether pupils should be stopped and searched if they are suspected to be carrying knives. He acknowledged that it is an “intrusive” power that can “alienate” people, and said it must be conducted in the right way and balanced with community engagement.Meanwhile, Will Linden, deputy director of the Scottish Violence Reduction Unit – which is credited with having helped halve the city’s murder rate – told MPs that “campus officers” can transform children’s attitudes towards police. “One of the biggest changes we saw in a single school is the first time we put a campus officer in the school,” he said.“And the campus officer role wasn’t to police, it was to engage, it was to mentor, it was to build and break down bonds between gangs, between the individuals and policing.”Mr Linden described how having full-time officers based in schools can have a secondary effect of encouraging youngsters to see policing as a career option.“That school in the space of one year had never had a single applicant to then Strathclyde police to become a police officer,” he said. “In the space of one year they had I think eight applications from the school to the police. We saw a change in attitude.”The education select committee, chaired by the Tory MP Robert Halfon, was holding a one-off evidence session to explore whether there is a link between the rise in exclusions and increase in knife crime.