A 2009 study by Matthew Theriot of the University of Tennessee compared student arrest and court records from one group of schools that had a school resource officer stationed on school grounds with those of schools that didn’t. Controlling for socioeconomic status, the researcher found that there wasn’t much difference in serious crime between the schools that had SROs and the schools that didn’t. Students at policed schools were much more likely to get arrested than students at unpoliced schools, but they weren’t any more likely to actually be charged in court for weapons, drugs, alcohol, or assault. (In other words, students at policed schools were much more likely to get arrested in cases where there wasn’t enough evidence to actually charge them with a crime.)
Students at policed schools were almost five times as likely to face criminal charges for “disorderly conduct” (which apparently didn’t rise to the level of an assault). In other words, when there was a police officer roaming the halls, students were much more likely to be arrested and brought into court for behavior that was disruptive, but not violent.