Underlayment grade is waterproof.
It is extremely inexpensive, and build time is very quick, although not the reported six hours. If all was precut, and there was someone who did it before, it might be a six hour endeavor, but with a class I would allow many weeks so THEY can solve the problems that come up. Groups of six to eight students are best, so a class of twenty could build three, if there was enough layout space. The manual is a great one, with clear and easy instructions. Get it first before you decide to try this task.