Before you delete a group, you must first remove all student tests from the group, as described in Manage Student or Group Test Assignments.
To delete a group, follow these steps:
From Setup > Groups, search to find group(s), or click the down arrow next to the Search button and select Show all results. Select the group(s) you want to delete.
Open the task list and select Delete Groups. Click Start.
Select the check box next to the group(s) that you want to delete. Click Delete.