Nearly 1,000 police officers are now based in schools, according to the Runnymede Trust (RT) equality charity.
Half of those are in London and are more likely to be based in areas with a higher number of students eligible for free school meals.
After a Freedom of Information request to moere than 40 forces in the UK, RT disclosed 979 police officers are based in schools.
Areas where police are deployed are also likely to have a higher number ethnic minority pupils.
Placing officers in this way can “facilitate the school-to-prison pipeline” for black and ethnic minority pupils, the RT claimed.
Dr Shabna Begum, head of research at the Runnymede Trust, said: “It is deeply concerning how normalised police presence in our children’s schools is, with no question over the highly-racialised and damaging impact excessive force can have inside a school setting.
“But, sadly, this is the predictable outcome when schools and policing are allowed to integrate in such intimate and unaccountable ways.”
A government spokesman said: “Schools are legally required to work closely with local authorities, police, and healthcare professionals to safeguard and promote the wellbeing of all children in a local area.
“The deployment of individual officers is an operational decision for police forces and a matter for individual schools, working together to decide the best approach.
“We have published revised Searching, Screening and Confiscation guidance which has been updated to emphasise safeguarding policies, providing clear advice to staff and parents on how and when to safely screen or search a child.
“The guidance also provides new advice on recording searches, informing parents, and supporting the voice of the child.”