That was my middle school ceramics project during student teaching too- slab
boxes. My time filler while firing was a little research project. I made a
web page of ceramic artist links and brought in a pile of books on ceramics.
We had 4 or 5 computers, and the students could search together, or they could
use the books, which was a faster way to do it. I told them to find an
artist who used slab techniques for a ceramic artwork and complete a critique
sheet about the artist/ artwork. I could send you a copy of the critique sheet
off list, but it is a very generic, look for art elements and the application
of design principles, describe mood or meaning kind of thing. Then they could
draw the piece.