We use this as a way for students to take responsibility for missing assignments. We did this as an RTI project in a high school size 500 students grades 9-12. Teachers (slips were color coded for each subject area) would hand in the slips. I kept track on an excel document. Once a student reached 2 missing assignments in a particular class, a note would go to them as a notice that they are currently missing 2 assignments in whichever class, one more and a phone call would be made to their parent/guardian. Once the 3rd missing assignment comes in, the student is pulled into my office and the STUDENT makes the phone call home to explain to their parent/guardian why they are missing 3 assignments in that particular subject area. A letter gets sent home along with the slips (which are signed by the student noting they are missing the assignment) so the parent can see the noticed slip as well.