[Using Sakai] Restricting access by group in new forums

[David Doria]

Hi all,

In Site Info->Manage Groups, have two groups. I want to create forum
discussion for each group, and disallow one group to see the others
discussion.

This seems to work properly for newly created forums, but in forums
that I copy from a different site, people in either group can see all
of the discussions.

In Forum Settings, I have set the Roles as follows:
Student: None
Group A: Contributor
Group B: None

Is there a way to restrict this access to existing forums?

Thanks,

David