Automatically set all folders to be "Read & Write"

Changing permissions without understanding the *NIX rules is an excellent way to wind up with an unbootable system. Don't change anything below your user directory.

 

edit: To remove personally identifying information not relevant to the thread.

 

Are you talking about the folder your teacher is sharing with you or you are sharing with him?
Either way only mess with the sharing settings in preferences and you won't do to much damage.
You cannot really make anything unbootable by setting too many rw privilledges, it would just make a system insecure. Still stick to sharing settings if possible.

You can use chmod or chown to change such settings in terminal.
Type "man chmod" for instructions but I would check out all options in sharing first because you still would need at least one command each time you deal with a new set of shared folders.

 

One can also make a Service using Automator that contains the chmod command. This service then appears in the Finder's Services menu, or in its right-click contextual menu.

There are plenty of examples on the web. Example google search terms:
chmod automator service