What you can do on Classlist varies according to what admin status you have as a member; ie whether you are a parent without admin rights or a Class Admin, Community Rep or Ambassador.
Staff members can have Staff Admin rights and don't have a parent account.
The Ambassador role is automatically given to the initial creator of the site, but can also be assigned to other key parents who play an active role in the school community such as PTA post-holders. Ambassadors can access all areas of the site, manage membership and can moderate and manage content.
The Class Admin role is usually allocated to someone who can act as the representative for the other parents in his/her child's class/year. If your school operates a system of Class Reps this role is perfect for them. Class Admins can approve parents and view most of the admin features on Classlist in relation to the class/year which they represent. They can also send announcements and create Community events.
Staff Admins have the same administrative powers as Ambassadors in terms of approving and managing parent members, but do not have any access to the parent side of Classlist. This means that Staff Admins cannot view, access or moderate parent-created content (such as group posts and comments, or Marketplace listings). Staff Admins do not see the 'Moderate Community' or 'Groups' admin sections either at all.
Parents can't communicate via private messages with Staff Admins on Classlist.
Staff Admins can send out Announcements and Community Events to any group and view parent comments on those.
If there is a need for staff to communicate with parents in groups and via private messages they would need a parent account, not a Staff Admin account. More info on staff using parent accounts on Classlist is here. Staff with parent accounts would appear in the parent member list.
Community Reps can use the admin features to create announcements and community events, but have limited access to the other administrative features. This role is suited for parents with a specific position in the parent community which may not be the same as a PTA position, eg Fair Funding Campaign Officer, Second Hand Uniform Sales, or just someone who is keen to help out from time to time. It can also be used to allow teachers with parent accounts to send announcements to any group. Community Reps cannot manage parent membership or view or moderate group posts or content