I would think 6 plates per student should be sufficient for whatever protocol they devise. We are up to 12 students now, so maybe 3 sleeves of plates?
To make Medium 21, add the following in order to a liter flask,
DIW (pure deionized water) 800 ml
K2HPO4 (anhydrous) 0.72 g
KH2PO4 (anhydrous) 2.16 g
Difco Bacto Peptone (not Proteose Peptone) 3.2 g
Difco Bacto Agar 12.0 g
Mix by swirling (no need to dissolve). Autoclave 10 min. Cool to 45–50° in a water bath, and pour plates about ½ full.