I use 2.8 (hoping to upgrade soon) but suspect the principle will be generally the same.
You can assign the supervisor to each employee or you could set it up for the supervisor (if they're required to complete the same course work) to see grades of their whole division. It takes a little work...
If you're using cohorts and already have them set up, create a group in each required course for each cohort (you can set up a bulk upload rather than setting up a bunch of groups in every course and then load it to each course). When you assign Cohort enrollment, choose the cohort group before you save. It will automatically add all the people in the cohort to that group. If you add people to the cohort later, you may have to update it...just edit the cohort and save it. If your cohort already is assigned to the course, edit it, change the group to your group for the cohort and save.
Now for the role...I created a custom role using the non-editing teacher role (Site Admin->Users->Permissions->Define role->Copy existing role, edit, etc...I took away some of the teacher permissions but left the ones allowing them to view the course reports, including the overview, logs, view grades of others and course completion status reports (there are a bunch). Then in the course, I add the new role to the people who need it. If you've set up the cohort with the supervisor in it as a participant, the extra role will allow them to see their employees and noone else and still allow them to participate.