From the brief: "Although there is substantial evidence that police officers in schools, also known as school resource officers (SROs), do not advance safety in schools, their presence in schools has increased dramatically over the past 30 years. It is estimated that only 8% of the violence-prevention programs implemented in U.S. schools meet a research-based standard, and only 44% of those few programs meet a standard of effective implementation. Therefore, the evidence reviewed in this brief covers a broad range of studies of the effects of police presence in schools and the racial disproportionality of those effects, and of studies that provide guidance for identifying evidence-based school safety strategies."