The workshop begins by having students observe the basic structure of the skull based on drawings and 3-D models. Depending on the class, a short sketching session (pencil/charcoal and paper) might be used as an introduction (10-15 mn.). The skull is built up as an overall solid shape which includes the jawbone. The eye sockets are pressed in place with the fingers, and during the second part of the workshop the other features are added and the bone shapes refined using tools. Some students may like to decorate their finished skull, say with a hat, or incised drawings.
Three hours is a little short to achieve a lot of detail with a complex subject like this, but it will give students enough understanding of the process for those students who are really interested in detail to continue working on their own skull for a little longer, perhaps at lunchtime or in another art class.
Materials (if I come in person I bring a lot of these with me):
clay-2lb (or 1kg) per student (air drying clay is good but ordinary pottery clay is fine too)
wooden boards
rags
plastic bags or pieces of plastic to wrap works between sessions
small supports, like small blocks of wood to rest the skull on while working on it
water sprayers
pieces of sponge
clay tools: some high schools have these, they need to be small and the ones for hollowing out are the most useful. If it is a virtual workshop and the school has no tools, the teacher and I can discuss what kind of everyday implements can be used instead.