Paul,
If you go to www.aliceprogramming.net, and click on the solutions to Chapter exercises and projects link, you can access not only the solutions but the "shells" as you call them -- the world with all of the objects in it correctly positioned, but without the code. You will need to contact Prentice Hall for access to this password protected area.
You are welcome to share these shells with your students, but please do so in such a way that they are not available to the general public.

Regards,
Steve