Pink Slip for Homework?

Have you ever heard of a pink slip for homework? Me either, but a teacher friend of mine recently told me about them and I've done a little research on the subject and found an article entitled "Effective Teaching..."  In this article they talk about pink slips.  What are pink slips?  Pink slips are a way to make students take accountability for their actions.  If a students shows up to class with no homework they must complete a pink slip.  On this pink slip students are required to give a reason for not completing the homework.  These slips can be used in parent conferences.  One teacher claimed to have a significant improvement on the amount of homework turned in.  You can see and example of a pink slip here.