Right -after much testing I think I have got this.
First of all, my bad ( I can't believe I used that term! - mea culpa would be more my style) for forgetting to enable group members only on my 2.4 dev site.
Here is what I think:
The course is set up like so:
Group A comprising students 1,23 and Group B comprising students 4,5,6 are put into GroupingAB
Group C comprising students 7,8,9 are put into GroupingC
Student 10 is not in any group at all.
Scenario 1:
Make an group assignment. Ignore the “grouping for student groups” setting (none) and in the common module settings, set it to separate groups / GroupingAB and available to group members only.
Result:
Only students in the groupingAB will be able to see the assignment; students in group/groupingC and student 10 will not. The gradebook shows 4 groups A,B, C and the default group. Student 10 has been put in the default group.
Scenario 2:
Make a group assignment. Set “grouping for student groups to “GroupingAB” and in the common module settings set it to separate groups/GroupingAB and available to group members only.
Result:
Only students in groupingAB can see the assignment; students in grouping C and Student 10 will not. The gradebook shows 3 groups: group A, group B and the default group comprising group C and student 10
Scenario 3:
Make a group assignment. Set "grouping for student groups" to GroupingAB. In common module settings, leave it as separate groups but grouping/none/and don't tick available for group members only)
Result:
Everyone can see and do the assignment. There are 3 groups: A, B and the default group. The default group comprises group C members and student 10 not in a group.
Scenario 4:
Make a group assignment. Set "grouping for student groups" to none. In common module settings leave it as separate groups with no grouping and available for group members only not ticked.
Result:
Everyone can see and do the assignment . The gradebook shows 4 groups: group A, B, C and the default group which consists only of student 10 who wasn't in any group.
Scenario 5:
Make a group assignment. Set “grouping for student groups to “GroupingC” and in the common module settings set it to separate groups/GroupingC and available to group members only.
Result:
Only students in groupingC can see the assignment; students in grouping AB and Student 10 will not. The gradebook shows 2 groups: group C and the default group which comprises members of groups A, B and student 10
TEST:
Scenario 6: A group assignment has the "grouping for student groups" set to "none" and the common module settings set to separate groups/GroupingC/available for group members only. Who will be able to access this assignment and how many groups will be displayed in the gradebook?