If a piece of clay is bisque fired with a chip of plaster in it, the pot breaks or a piece pops out because of the expansion of the plaster after firing. When we used plaster bats for pots in the classroom I lost too many pieces because chips of plaster kept getting mixed into the reprocessed clay.
As an alternative we place our pieces to dry on cheap unglazed 6 x 6 imported floor tile (quarry tile). These are nearly as absorbent as plaster, do not warp, and chips are not a problem. They can be soaked and washed easily. I set them to dry vertically on a board with a bunch of dowel rods separating them during drying.