We have it in the band policy that if you are not prepared for rehearsal (no music, horn, pencil) that it is a 30 point deduction on the daily grade. Our grading policy is based on the phrase "Student must demonstrate..."; if they are not prepared for the day, they can't demonstrate their knowledge of the material on that day.

Usually if it is the first time the student forgets something, or if they only forget "once in a blue moon", we give them a break with a reminder that the next time it goes in the gradebook. If they forget again within a week to week and a half the deduction goes in the gradebook each time they forget.