Shellac is a great finish. It dries fast and if used correctly, can build up a decent protective layer on wood very effectively. It is not resistant to water or alcoholic beverages as varnish or lacquer are, but it is very forgiving to apply. Perhaps more importantly — it keeps my students busy. This last point needs some clarification.
Towards the end of the trimester, when my 9th-grade students are ready to apply a finish on their box projects, shellac becomes an indispensable ingredient in maintaining a healthy teaching atmosphere. Finishes such as oil, oil-varnish, wipe-on varnishes and pure varnishes take time to dry, or more accurately, polymerized. That means, that if a student is applying a layer of one of these finishes at the beginning or the middle of class, they have nothing else to do until the end of class, as they need to let their project dry for a day.