Hello NeuroPlos,
This is author TM. GG and I are constantly brainstorming invertebrate preparations that can unequivocally demonstrate action potentials that are the most humane with the most benefit. The cockroach leg preparation is not perfect, as you still have to cut the leg off of the insect, but we've found it's the "least invasive for maximum benefit" as the legs can grow back in juveniles, and the cockroaches can get around fine with 1-2 legs missing. We are also exploring other pharmacology experiments that don't use the cricket. It's a tough problem; you need living neurons to demonstrate electrophysiology, and neural tissue cultures are just not feasible for classroom experiments. Below is an except from the form we give students and their guardians:

"The equipment to be used, as well as the lessons to be followed, are experimental prototypes currently under refinement. The experiments that you will conduct are identical to or are variations on the procedures that you have seen demonstrated in class: invertebrates will be anesthetized and prepared for recording, nerve signals will be recorded, and various stimuli (tactile, thermal, light) will be applied to the preparation....
Please note that this is a research project designed for the purpose of improving education. You will benefit by gaining additional information about the nervous system and about the proper care of live animals (invertebrates) in research....

Risks are minimal:
-­‐ Some sharp tools (pins and scissors) will be used (you will receive proper instruction in their use);
-­‐ The invertebrates are not poisonous, do not sting or bite, and were purchased from commercial suppliers or raised in
the laboratory expressly for this use;
-­‐ You might experience mild emotional discomfort caused by exposure to the invertebrates (cockroaches or
earthworms) or by the surgery (removal of a cockroach leg or exposure of the earthworm nervous system – both done while the animal is anesthetized and following scientifically accepted and humane procedures). If such discomfort occurs you will be free to stop participating at any time without penalty.
Your participation is entirely voluntary. If you decide not to participate there will be no negative effect on you or your relationship with your teacher..."