An analysis of recent school shootings by students has revealed a twofold problem in preventing such violence: the lack of counseling and social services in schools and ineffective means of preventing bullying among students. Schools should aim to have a maximum of 150 students assigned to each school counselor. Bullying prevention is critical in elementary schools, because the escalation of bullying behaviors and the unresolved psychological impacts for victims of bullying become "time bombs" for extreme violence by both bullies and their victims as they move into their teen years. The use of school resource officers (SROs) is another means of countering school violence. An SRO program is a collaborative effort by specially trained police officers, educators, students, parents, and the community to offer law-related education programs in the schools for the purpose of reducing crime, drug abuse, and violence, which in turn provides a safe school environment. SROs also provide a police presence in the schools; however, the effectiveness of such a presence requires that SROs be trained in youth development and psychology and work under strategies of student management developed in cooperation with school staff and parents. Other means of enhancing school safety either through prompt responses or prevention are the digital mapping of a district's school interiors and exteriors to facilitate logistical planning in response to a violent school incident, as well as the installation of video cameras at various locations around the school.