Subtleties in the policies, such as defining teacher duties, for instance, can lead to safety and security problems for the very children the policy is designed to protect. Contracting with children to obey certain directives is one way schools attempt to foster a sense of responsibility on their charges. By the same token schools cannot delegate their duty of responsibility to their students. If the school security and safety policy is not managed by the staff who has charge ot the students, or is incomplete in its set of instructions to its teaching and administrative staff, then to blame the child who may be injured because of a breakdown in following procedures by saying he or she knew but didn't do, is only an attempt to cleanse itself of liability by delegating duty and authority to the very person for whom the policy was designed to protect. Alas, there's the rub.
Security is basically an easy task.
People don't become victims unless they make themselves victims. This holds true both for the individual who suffers an injury from an assault and the defendant company upon whose premises the assault occurred. I know that it is difficult for the average human to maintain constant awareness of his or her surroundings and security related actions, and I understand that some people have a difficult time displaying indications of self-assuredness and security awareness. I also know that sometimes security can become an expensive proposition for companies, although cost can be a relative matter. But that does not mean that simple, reasonable, and practical security measures cannot be taken.