read only Public issue

I have an OD server running AFP file sharing. It is 10.4.11 and the Leopard clients are 10.5.7 When faculty post a file to their public folder and have students log in and retrieve it. They copy the file as read-only. Is there a way to force the client to make all files copied to its local drive read/write ? Apple said to make the folder a zip file or change Public to read/write but I figure there has to be a better way. Some faculty have many folders in their Public folder and converting them all to zip files would be time consuming and of course change Public to read/write for everyone wouldn't work either. thanks