It would be nice to have the ability to "wipe" a lesson after you are done, much like cleaning the whiteboard in a physical classroom. I use the same lesson in multiple classes and I have had many times when important information (like the answer to a practice problem) was given away too soon because I had already written it on the slides during the previous class. Perhaps we can have a single lesson that saves multiple instances of itself for multiple classes? Teachers can select the lesson then select the instance they need to present!