Your sorority board comes up on the first page of a Google search using the exact words in your signature. It's nowhere near private.
If you want to make your sorority's message board private, see:
http://www.phpbb.com/kb/article/create-a-private-forum/
http://www.phpbb.com/community/viewt...f=46&t=1315605
Something dated from this year (January 2010) on the college message board is relevant, particularly when it involves chapter finances.