This is a good way to begin the class and get the students thinking about how markets work. It teaches students to draw and understand step-function demand and supply curves, and it gives them useful practice for later, more elaborate experiments. The experiment and lab report can easily be skipped for an intermediate class, although assigning the discussion and homework sections may be a good idea. These three experiments are easy to do and fun for the students. You may want to pick one to accompany the appropriate material.
Students get to explore the implications of putting a tax on the buyers versus the sellers.
Skeptics are finally convinced of the equivalence of a tax collected from demanders to a tax collected from suppliers. Prohibition Students seem to really enjoy this experiment, perhaps because of the topic. Fundamentally, it is a nice application of some basic competitive equilibrium theory. In addition to learning about the effects of market controls like price ceilings and floors, students learn to define and measure voluntary and involuntary unemployment. This experiment has been very successful in intermediate classes.