Hi Nana
We use Groups a lot as we train apprentices that are organised into groups (I call them Teaching Groups) We have added a field in the user profile "Teaching-Group". This data is used to add them to relevant Dynamic Audiences that are then enrolled into specific courses using Audience Sync, where you can easily create a group. The Course is set up to run Activities as Separate groups to keep the users separated in their groups.
As Craig has said, you can produce a course completion or Activity completion from inside the course. Or look at activity results, such as quizzes, as a group.
Using the Profile field, you can run a Site-level Course completion/progress Report using the Teaching Group. This provides a high-level report to help you easily identify those who need the most assistance, before delving deeper.
Happy to help.
Cheers
Stephen