Craft Modeling Clay
How it sets is the whole decision. Plasticine stays soft indefinitely, so it is reusable and ideal for practice and stop-motion but useless for anything a student wants to take home. Air dry hardens on the bench over a day and takes paint. Polymer clay cures in a domestic oven and finishes hardest, which suits jewellery and detail work but needs supervision. See ceramics, mosaic tiles and art supplies.