What's the "pass" in this situation?
I believe the "pass" here is a letter showing that she is meant to be in that class. It wouldn't be a lavatory pass or a hallway because this is the first day for Bella at a new school. I am unsure what it's like in other countries, but in the United States, students are enrolled in certain classes, and teachers will have a list of their students for each specific class. Bella may need a pass to show her teacher that she is enrolled at this school and that she is supposed to be in this class at this time.