When event-based experiences are added by a school admin, allow user to assign this event to multiple schools

We are having a district-wide career fair where we will bus all 8th graders to the event. As a district admin, I'd like to be the creator of the event for the whole district and provide a QR code to the schools to register attendees. It will not let me create the event without selecting a school first. But this event affects multiple schools.