PC Andy Best has been stationed at Waltheof school, Sheffield, for three years and believes his presence has had an effect on pupils' behaviour.
The officer took on the role when asked by the Youth Justice Board to pilot the Safer School partnership scheme. Now he says that truancy and criminal offences have dropped in the past three years.
PCBest and staff at the South Yorkshire school have discussed with students the reasons they are getting into trouble.
A similar scheme in Liverpool is also having results. Michael Ward, a police constable, is based full time at Parkland high. He said: "We have seen truancy drop by 23 per cent, exam results are up and the school applications from feeder schools and other schools in the area have increased.
"Pupils' attitudes towards police officers have changed, too. The other day I was driving to a meeting when I heard a group of youngsters shout 'Mike, Mike'. A few years earlier they would have been swearing at me.
"The Government wants facts and figures but some work is hard to quantify.
You should see the amount of birthday cards and Christmas cards I get."
Two years ago, on Hallowe'en night, there were 32 recorded crimes locally.
Last year, after much work with students in the classroom and a school disco held on the same night, only eight were committed.
"Having a police officer based at school is such a simple but great idea. I think all schools should have one," he said.
Chris Dark, head of Peers school, Oxford, said his school had a similar arrangement: "The initiative between us and the community police, including an officer coming in once a week, has made sure that we can work on conflicts between students together, inside and outside of school."
An evaluation of the scheme last year found that more than four out of five pupils in schools where police are based felt safe seeing officers patrolling the corridors.
However, the report said that most local authorities had difficulties finding police officers who would do the job.