Since I always have multiple grade levels and multiple stages of clay at ceramics time, I had to find a way to keep different classes work organized. When I moved into my fancy schmancy new art room, I was able to order a ceramics cart like this one which has made transporting and storing clay sculptures in progress much more manageable.
Even still, I usually have every single shelf of this cart full, plus the storage shelves in my kiln room, plus multiple trays or copy paper box lids of sculptures to be glazed or returned. In order to easily see which class of sculptures is which without picking sculptures up and flipping them over to find a class code, I made a set of class code tags that can be easily clipped to any shelf, box, or tray using a binder clip. I laminated a set that includes one tag for every class we have in our school, color coded by grade level of course, and I keep them in a bag clipped onto the side of the cart.
Inside the bag with the tags I also keep binder clips that are exactly the right size for the shelves. When it is time to store work on the rolling cart I clip the class code tag to the shelf and students know on exactly which shelf to store their unfinished sculptures.
After bisque firing I move the sculptures and tag to a tray that I can carry into my room, which leaves more room on the rolling cart for greenware. When sculptures have been glaze fired and are waiting to be returned to students I move the tag and sculptures onto a shelf in my kiln room until it is time for them to go home. This system keeps things organized and helps my art teacher colleague find her things if I have fired them while she was at her other school. Even if I had a sub and wanted to leave glazing for the day, all I would have to do is let them know which class code to look for.