Feature availability varies by program.
You can remove student tests from a group to delete test data for completed administrations.
From Setup, select Groups.

Type a group name into the search field, and click Search.

Click the checkbox next to the group to edit.

Click Select Tasks, select Add / Remove Student Tests in Groups, and click Start.

Click the checkbox next to the student test under Assigned Student Tests.

Click Save.

After you remove all student tests from a group, you or an authorized user can delete the group.