Many school districts have community policing available, not all. It depends on the size of the community. Bigger urban centres tend to have the liaison available right in the school system. In rural high schools there's a much bigger population. They have more conflict, more issues with respect to drugs coming into the school, or concern about weapons. So it does depend on the province and the municipality and the type of school they have and the issues they are facing.
Most district school boards have a very strong relationship with their safety counterparts in the community, whether that's the local police or working with social service agencies to support the children. It would be very uncommon to see a school system now that wasn't connected to all those social services to support the issues they're facing, including the police in some fashion.