So are most of these high school sororities and fraternities at private schools or large public schools? I went to a very rural school were I don't think this idea would have flown. The Key club and Keywannettes behaved somewhat like social clubs, however. They didn't really do much service, they just threw social events for themselves.

Their membership was open but I never bothered joining. They would drive out the "uncool" people by excluding them from stuff... I can't imagine my high school allowing this, however...
I was also reading about how in the early days of fraternities and sororities there were no rush rules, so the groups would begin recruiting in high school. Sometimes they would pledge and initiate high schoolers! Part of the reason for forming the NIC and NPC stemmed from this problem...
Does anyone know whether people still colonize high school fraternities and sororities? Do they get shut down frequently nowadays--it seems that a lot of mothers were in them but not so many GCers...
And on the Sweet Valley tip:
http://www.randomhouse.com/sweetvalley/#
The website also states that Francine Pascal attended NYU.