Principle of reasonable trust. The principle of reasonable trust holds that if the victim or the third party reasonably believes that they will take appropriate actions, and if the victim or the third party takes inappropriate actions, causing damage to the result, the actor will not be criminally responsible for the result.

First of all, the school is closed, and it is in physical education class. The student has every reason to believe that there will be no elderly people other than teachers and students in the school when playing badminton, and the student should not bear the medical expenses for serious injuries caused by negligence. Students' complete trust in the school depends on its closed management. The doorman won't let irrelevant outsiders in casually. The school is responsible (the school can investigate the fault of the doorman), and of course the elderly should also bear certain responsibilities.

Personal views are for reference only.