I've worked with PMC in a workshop setting. I can't imagine working with
a class full of kids with this material unless they help pay for it
themselves. It is extremely expensive. It also requires the special kiln
for firing. Tiny and expensive tools are also required and lots of
patience. You can re-wet and continue to use the dried pieces but it's
difficult to keep them moist. We used saran wrap and kept all materials
wrapped at all times. As far as waste? ???????????? I don't know how
you would control that issue . If your students are anything like mine
they real don't care. It's exciting material to work with , and we made
some really cool things, but I wouldn't use it with kids.
The book I have (which I'd be willing to sell--brand new) is Working
with Precious Metal Clay by Tim Mcreight. Gives tips and techniques,
some for home made tools too.
Hope this helps,