I call this "Dewey of the Month" but it can really be any length of time - day, month, week, fortnight, etc.
In trying to highlight my nonfiction section to my students, I liked the idea of highlighting an area that was popular (at first) and then delve into the lesser known areas. I've displayed 3 Dewey circles on a bulletin board in the library, as well as in a display outside the library. When I introduced it to students, I encouraged them to find the section and, if they checked out a book from it, to fill out a slip that would be drawn for a monthly prize. Students now are more interested in checking the board to see what type of Dewey numbers are highlighted, as well as finding those areas a little easier (and paying more attention to the shelf labels!).
Another idea is to display the circles on the actual shelves itself, to draw attention to them.
I hope you find success with a Dewey program and having your students become more proficient in finding nonfiction books in the library!