Categories are listed in order of creation, but the relevance changes during the class. As an instructor, I'd like to be able to drag the most relevant categories (e.g., the homework or exam that is coming next) so they appear near the top of the list.
It would also help to be able to set categories for future use (and any preloaded posts) to invisible. (e.g., an open or closed eye at the left of each category name.)