Our students each carry their own bathroom pass. They are allowed to use it once per day to leave a class without a penalty. At the end of the day the teachers all redistribute the passes to homeroom teachers to pass back to students for the next day. This pass is their responsibility. Each homeroom copies their passes onto a different color of paper for easy sorting and we write student names on the back of the card before laminating so they can't use someone else's pass if lost or stolen.
Pass says - You may us the restroom without forfeiting your pass before the tardy bell, between classes, at lunch/recess, at end of day. Without this pass there will be a penalty for leaving class to use the restroom.