When police officers are stationed in school hallways, a minor violation of school policy can land a child in the system, sending them into a cycle that could be avoided. This is why schools with police officers see increases in crime. In many cases, officers are not trained in the fields of education or developmental psychology, so they handle situations based on the way they have been trained to handle adults. Police officers have more difficulty determining what is a legitimate security threat and what is simply a disciplinary issue than teachers and administrators.
It has also been noted that minority students and students from low income families are disproportionately affected by the placement of police in their schools. A chapter of the NAACP in Texas reported that black students in the Bryan school district had four times as many criminal misdemeanor citations as white students. In a school district in New York, law suits have been filed against officers who arrest children for noncriminal behavior.
Based on observation of the practice in action, it would seem that placing police officers in schools is a use of resources that creates a more penal school environment for students and puts them at risk of being put through the juvenile justice system for minor disciplinary offenses.