When a Classlist administrator invites a parent to join Classlist using an email address, the invitee becomes an 'Invited Parent', also known as a non-member contact, until they join the site. Although this invited parent status is really intended as a temporary phase, some parents forget to sign up or just aren't sure what to do, so they remain invited but not signed up. To ensure that these parents don't miss out on important messages about what's going on at their school, the Classlist system includes them in any important communications created by admin users at their school; these are only messages of whole-school or whole-class community interest such as Announcements and Community Event invitations.
The system works in the same way as a mailing list: other parent members cannot see an invited parent's details on their Classlist site, nor can they get in touch with invited parents via the site and vice versa. Only certain admin users can see that someone is included as an invited parent. Invited parents therefore miss out on most of the benefits of Classlist, but are still kept in the loop. There is more information for admin members about managing invited parents here.
If you have been invited to Classlist and do not wish to hear from your PTA or Class Admin via Classlist, you can click the 'opt out...' link at the bottom of any email (see image below).