I attended a batik workshop, where we used 4" foam blocks to transfer the
hot wax to the fabric. We did use exacto knives for cutting away the
negative spaces in our blocks. Depending on the number of students in your
class, you may be able to keep better control of the knives and their use
by limiting the number of knives and asking students to use them at a
"center" like in elementary.
North Winneshiek Comm. School
Decorah, IA 52101