To remove a user from a group select “Manage > Users and groups” from the top menu and click on that learner from the list to access their profile page.

On the user’s profile page, in their details panel, click "EDIT" in the Group memberships panel. Then click the "REMOVE FROM GROUP" button next to the names of the relevant groups that you would like to remove the user from. Finally, click SAVE to confirm the removal.

The user will no longer be able to see the courses available to the group within the Course Library and from associated group assignments. However owners will still be able to view results from previous attempts.