How many times have parents asked their children this very question only to hear the response, "Nothing," or "I don't know"?
This type of closing is a beautiful way to open communication of learning with parents. The best is that the response comes from the student, but it is also an assessment piece for the teacher.
My students are required to have their parents initial all of their homework, so when the students take home facts about bats today as math homework, the hope is that the conversation will turn to the fact that the students created line graphs, that the little brown bat population is declining rapidly, and that graphs can show us a lot of data in an easy picture.
Now, not only do parents hear what happened in school, but the students are once again practicing communicating their leaning and understandings in a real world way.