Fresco techniques can be explored by pupils of all ages. Use fine white plaster of Paris, which can be tinted with powder colour during mixing.
Combine fresco and relief by giving each pupil a shoebox in which they insert a thin slab of clay in the base. Impress a repeating border around the edge of the slab with found objects. Pour a mix of plaster and water into the box covering the clay to approximately one centimetre depth (young children should not be allowed to work with plaster unsupervised.) On hardening, remove the clay and card from the slab. The reverse side will now have a raised border enclosing a flat surface which will take paint.
This can now be decorated, using a pre-prepared "cartoon" in the method of the old masters, by flooding water-based paint onto the surface. Work from light to dark, and the paint will be absorbed into the plaster. Each panel could represent an aspect of the pupil's life in school (refer to Giotto's "Betrayal" and Diego Rivera's mural paintings for sources). Assemble the pieces together by sticking them to a wall, using impact adhesive.