"Exit cards are used to find out what students know or have learned during a lesson or unit of study. Information gained from the exit cards can be used to assess student learning, form groups based on readiness, and help plan your instruction. At the end of class, give students a question, a sentence starter, or a problem to solve that relates to your current unit. The students provide their answers on a file card, sticky note or scrap piece of paper. The exit cards should take no more than five to ten minutes to complete and are handed in as the students leave the classroom."
Reference: Regler Educational Ressources
This resource also provides teachers with links to a number of Exit Card Websites where you can find examples of Exit Card questions and prompts.