It's bad to put a snake in someone's bed.
Jessica attends a boarding school where she is bullied by one of the girls named Annabelle, who is in her dorm.
Jessica wants Annabelle to stop bullying her.
Jessica tells the headmistress about the bullying, and asks to be assigned to a different dorm.
Jessica catches a garter snake and puts it in Annabelle's bed one day, scaring Annabelle very badly.
Annabelle and Jessica no longer share a dorm or any classes, and Jessica is no longer bullied.
Jessica is expelled from the school and never sees Annabelle again.