Each day, at the end of your lesson, have the students write their response to the exit question. In my classroom, I have the students write their answers on small slips of paper, and I save them. This helps me know if I need to reteach the whole class, provide small group interventions, or just keep moving on. You could use scrap paper, or even have them write on a whiteboard to save paper.
This is a great tool for daily formative assessment to make sure your students are learning the essential skills!