Lauren,
Like you pointed out, that is controlled by the setting each student has in their profile. At the forum level, you can force everyone to be subscribed, but you can't force everyone to be unsubscribed.
By default, everyone's profile is set to subscribe them to any forum they post to...the Forum auto-subscribe setting. So, when a student posts to a forum they get subscribed and most don't realize it....even though there is a statement at the bottom of the posting screen, most don't even see it.
I solved this problem on my sites by changing the Forum auto-subscribe value in the mdl_users table of the database from 1 to 0. This makes the default setting for Forum auto-subscribe in the user profile "No: Don't automatically subscribe me to forums".
Changing this value won't impact any existing user profiles, but it will change the default value for any new accounts. Your existing users will need to change it for themselves, unless you are comfortable doing a query on the database to change all of them.
Steve
Thanks, this is just what I needed to know.
Thank you, Lauren