As far as I can see, there is no way to do the following using Forums:

• Each semester, student groups (3-4 members/group) are assigned to follow different news themes from Germany (e.g. music, sports, business, etc.).
  
• Each week group members post stories in their group forum.
  
• Other students (not only those in their own group...but other groups too) read, rate and respond to these postings.
  

I tried creating forums using "Visible Groups"...but then non-group members could only read and not rate or reply to posts.

I tried adjusting Permissions to allow students to rate. This allowed non-group students to see the "Rating" option...but when they click it, an alert box says something like "You need to be a group member to rate."

I would prefer not to use "No Groups" because then I will have problems with students posting in the wrong forum.

Any work arounds would be welcome.

* Thanks to Mary for suggesting I post in this forum!