I was reading a book on Google Books, "Alpha Xi Delta Sorority" from 1905. It's a collection of letters and essays and "reports" on from the early years. In one section, they addressed High School sororities and how they are different from collegiate sororities/fraternities. Though it was written over 100 years ago, I think that it still applies:
"In school, groups of girls form into little "cliques" and it is from the most influential of these groups of congenial girls with the same circle of friends that a sorority is formed. Its object in nine cases out of ten is social, purely. Dances, afternoon gatherings and theater parties are its aims; a jolly time its one ideal. In most High Schools, only seniors are eligible for membership, so that the girls have only a short time to really know one another. At the end of the year they separate, some to go to college some to enter business, and all to broaden their horizon beyond the limits of school life.
How different this social club, for it is nothing more, is from our college sorority. In the one we are careless girls, in the other women; in the one we seek only for pleasure, in the other for something nobler; in the one we think only of ourselves, in the other we are taught to think of others; in the one we seek amusement, in the other truth.
In the High School Sorority we pledge ourselves to nothing, in the college to a life of devotion and loyalty. The two are alike in name only. In the former you know a few girls of your own age in a superficial way for one year, in the latter, you know women older than yourself to whom you look for example, and younger than yourself who look to you for guidance,; during many years, for what girl after four years of intimacy of sorority life could ever forget her "Frat"?
In the High School Sorority there is no idea of improvement of mutual help or of ethical elevation. In a National College Sorority there are all." *
Btw, there are books for several of the NPC sororities if you look at this link:
http://books.google.com/books?id=p9sTAAAAIAAJ&dq=%22alpha+xi+delta%22+manu al&source=gbs_navlinks_s
*Official Organ of the Alpha Xi Delta Sorority, November 1905, Vol. III, pp121-122, Edited and Published by Eta Chapter Syracuse University Syracuse New York Office of Publication 707 Irving Avenue, Syracuse New York.