How does a teacher know if their students learned anything? Did they understand the day's lesson, and will they be able to recall and use it in a week? A month? A year? We begin by talking about different types of formative assessments, which are used to see how well a lesson was understood (3:20), then about how to distinguish information from similar concepts that have different rules (9:45), and then how to keep the knowledge fresh months down the road (19:45). Joseph gives April Fool's Day stories, and then we play a Numbers Game about big cities.