In Williamsburg, Virginia, where I live, the fraternities and sororities of The College of William & Mary invite new members in (and leave others out). What's in and what's out translates cunningly into who's in and who's out.
The Christians in Jerusalem’s early church were in crisis. Should they admit gentiles into their fellowship? Could gentiles be believers? Resolution of these questions did not come easily, but finally the Jews swallowed their pride and begrudgingly allowed the gentile outsiders to come into the fold.
When I was in first grade, teachers assigned students to reading groups based on how well they could read. They would name all the groups after birds so that everyone would feel equal, but you could always tell how well you were doing by what bird your group was named after. There were the Eagles, the Robins and the Pigeons. The Pigeons were not reading War and Peace