In Moodle 2.2.2+
Groups and Groupings are set up in a course.
Several chat topics were added and each was assigned a specific grouping.
"Everyone can view past sessions" is also set to "No" ( in the settings of the chat).
Group mode is set to "Separate groups".
When I log in as a student belonging to Group 2 (Grouping 2), I can still see all other chat rooms and logs.
This Groups/Groupings option works fine with Discussion Forums, but is not functioning with Chat.