"Beginning in the fall of 2012, Princeton University will prohibit freshmen from affiliating with a fraternity or sorority or engaging in any form of "rush" at any time during the freshman year.
The decision to institute the ban is being communicated this week to all returning Princeton undergraduates by President Shirley M. Tilghman, who made the decision based on recommendations from a student-faculty-staff working group on campus social and residential life that submitted its report last spring. The decision is being communicated to all entering freshmen and their families by Vice President for Campus Life Cynthia Cherrey and Dean of Undergraduate Students Kathleen Deignan.
In addition to prohibiting freshmen from affiliating with fraternities or sororities or engaging in the recruitment/membership process known as rush, the ban will prohibit students in the other three classes from conducting or having responsibility for any form of rush in which freshmen participate. As recommended by the working group, there will be no prohibition on membership in fraternities and sororities after freshman year, although the University will continue its longstanding policy of withholding official recognition for such organizations.
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In their letter to entering freshmen, Cherrey and Deignan pointed out that for most of Princeton’s history, membership in fraternities and sororities was prohibited. These organizations began to reemerge at Princeton in the 1980s, although unlike at many other campuses, none of the fraternities or sororities at Princeton has houses. All Princeton freshmen and sophomores live on campus in residential colleges, as do some juniors and seniors, while most juniors and seniors take their meals at off-campus independent eating clubs while continuing to live in University housing....
Approximately 15 percent of Princeton undergraduates participate in four sororities and about a dozen fraternities.
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The name "rush" comes from the unraveling of fraternity and sorority recruiting, which became earlier and earlier over time. Here's an old paper on the subject:
Mongell, S. and Roth, A.E., "Sorority Rush as a Two-Sided Matching Mechanism," American Economic Review, vol. 81, June 1991, 441-464