In Vancouver they're called 'School Liaison Officers' . In Vancouver, for 65,000 students spread over 17 secondary schools (and probably some elementary schools) they consist of one sergeant and 15 constables.
Taken from the Vancouver Police Department website:
"The common goals of Canadian School Liaison programs are:
prevention of crime and the enhancement of community safety through education
promotion of the police as an accessible community service
elimination of barriers between youth and police
investigation of offences and enforcement of laws
promotion of policing as a career"
- "The officers are there to:
deliver safety and crime prevention lessons to
students, staff and parents.
- act as a legal resource to students, administrators and staff
- counsel and talk informally with students
- work to enhance the safety and security of the school
- coach teams, join clubs and escort field trips
- investigate criminal offences relating to the school and its population
- serve as a liaison between the school and the criminal justice system"
In the eyes of the public: to check for drugs, and keep an eye on gangs. But I assume that they would attempt to prevent massacres, as well.