They cannot as just a "All School" User. You would need to add a persona role in order for them to have access to the Groups navigation in the navigation bar. To add this the best suggestion is to add the Friend Role. This way they do not have access to everything any other Role has access to.

To add a Role or Roles to a User Navigate to:
1.    Core
2.    User/Access
3.    Profile
4.    Manage Roles
5.    Click into the Role you are looking to add the User to
6.    Members
7.    Add
8.    Find the name of the user, click the >> to add the user
9.    Save & Exit


1.    Core
2.    User/Access
3.    Profile
4.    Edit User Profile Data
5.    Find the User
6.    Scroll to the bottom left System Information
7.    Select Role Membership 
8.    Select Edit
9.    Select the Roles you are looking to add to that specific user
10.    Save & Exit

To Clone a Role, see How do I create a clone of a role?