How do I give school staff read-only access?

From the School Administrator manual, "Inviting School Staff (Read-Only Access)".

Covered as part of Members — Parents, Password Resets, and Student Links above — staff invites are sent from Access (+ Invite someone new). A staff member (e.g. a teacher, counselor, or the school nurse) gets browsing access to the full roster with no edit controls anywhere, and no "my kids" concept the way a parent has. They're also a valid target for Document Library, Notices, Permission Slips, and Polls — you can address content "to all teachers" or any other staff role, not just to families by grade or by name (see Audiences (Targeting)).