Why schools make students do these advanced woodworking projects when they have slashed shop teaching budgets really infuriates me no end. The students have neither the expertise, or the resources to do a workmanlike job of this, and end up being alienated towards learning woodworking or any other craft because of this idiotic baptism by fire- another example of schools not wanting to do their job.
Excuse me, now that I'm off the soap box, I've had to help many neighborhood kids with similar projects, and have tried to salvage their egos and sense of accomplishment and show them the craft can be fun after all, but like everything else, crawl before you walk, walk before you run.
As Henry pointed out, special plywood that will curve is available, but you're not going to want to buy 32 square feet of it for your onetime need.
The way to do this is to glue up very thin strips of wood or wood product so as to make your own "Plywood", and do it around a form. Expanded foam block will suffice for a form, just obtain the thickness needed and cut out the desired shape or profile- a coping saw or electric carving knife will do.
The strips in fact can be made from card stock, shirt blocking, single-ply heavy duty cardboard, etc. as well as wood obtained from craft stores. Butter the number of plies for the thickness needed with white glue and wrap around the form. Tape or pin in place to hold until dry (do a "dry" run first- pun intended). The result, when assembled to the neck, and capped top and bottom will be very solid- you may also put glue blocks inside the body perimeter to aid in capping the instrument.