If the contaminate is plaster, the clay is irretrievable. Plaster in clay causes unacceptable defects when fired. Your presence in class is required. The interaction with classmates enhances the studio experience. The above information is also intended for independent study students in ceramics.
Ceramics can be a demanding discipline.
In the first years of study it is not unusual to find students with uneven levels of accomplishment. Some have good hand eye coordination and mastery of tools, but an undeveloped design sense. Others may have great ideas but cannot execute them in clay. At any level there is room for improvement, instructor included. Clean your work stations and tools at end of each session.