The diary is the thing being sold. Moving one lesson moves a room, a teacher and an invoice at the same time, and that is where almost all the school's paperwork is born.
Last-minute cancellations need a rule. Twenty-four hours ahead it stands, after that it is paid for: written into the system, it stops being negotiated on the phone.
Ten-lesson cards and monthly fees sit badly together. Offering both requires an account per student, or nobody knows at month end how many lessons are still owed.
Teachers are paid for the lessons actually given. A list that draws attendance and pay from the same source saves half a day every month.
Room allocation here is a question of acoustics. Two voices side by side interfere, and putting that in the room plan prevents the argument before it starts.
The end-of-year recital is a project apart from the teaching year. Sign-ups, running order, piano accompaniment and hall hire are managed like an event with a fixed date, not like another lesson.