After the recent spate of shootings at schools, an elementary school around here reviewed its security measures (locked doors and security cameras, I think) and decided that a new rule is in order: No visitors/parents allowed without an appointment. The top district official has said that if this rule proves "effective," it might be instituted at other schools in the district.
First of all, define "effective" and tell me what criteria will be used to determine whether this appointment rule is "effective."
Secondly, rules are made for the people who follow them. People who shoot up schools don't follow rules.