When I taught ceramics I recycled clay as we went, which means I did the following:
Each pair of students received a cleaned out spackle bucket (or you can get big white buckets with lids from your local bakery, usually for nothing, as some of their supplies come in them). It is important that the buckets have lids. As kids worked in clay, they threw their scraps in their buckets, making sure the buckets were airtight. We rarely had clay dry out. (I doled out x amount of clay to each pair of students, and until their buckets were totally empty they didn't get any more clay). If in their buckets, clay started to get hard, they were encouraged to spritz it with water, then put on the lid.
If you have projects that dried out, that were not going to get fired, I had them put the dry clay in a separate bucket that was for dried out pieces only (and labeled such), and we added lots of water to break the clay down.
Then to recycle the watered down clay I made plaster batts. Essentially on junk week in your town, go around and get all the drawers out of dressers that you can. You then fill these drawers up with plaster, making sure to have a smooth surface. When the plaster dries, you have a plaster batt, upon which you can put the slurry that the dried projects will eventually become. The plaster soaks up the extra water, and within a few hours, you turn the messy blob over, and have the batt soak up the water from the other side, then you wedge the clay, return the clay to thei students to put in their original buckets.