The org's class sessions (top-level rooms, newest first) for the school UI.

A class session = a VoiceChatroom with organization_id == this org and parent_room_id NULL (breakouts are its children, not separate classes). Owner/admin/teacher of the org (or platform staff) only.

Optionally scoped to one section; a teacher with no explicit group_id defaults to the sections they teach (see _resolve_class_scope). Rooms with group_id NULL — everything from before the column existed, plus school-wide sessions — are INCLUDED under a scope by default, because a section filter must not make a school's history disappear. include_unattributed=false narrows to rooms explicitly attributed to the section.