BuddyPress.org

Sounds very interesting. I’d be curious about (a) Whether users can apply for membership in groups, which group admins can then approve or deny (i.e. shift the burden to users) and (b) whether groups can have grandparent-parent-child-grandchild hierarchies (e.g. Class 1B is a child of all first grade classes, which is a child of School Z, which is a child of School District Q, etc.)