Yale University's Old Campus is a genteel assortment of Gothic, Gothic-revival and Georgian architecture circling a graceful lawn, with a flash of Tiffany stained glass, in a scene so picturesque that it has served as a model for other universities.

It is here that many first-year women students live when they arrive at Yale. It was also here, in the black chill of an early autumn night this academic year, that the quiet was punctuated by a single line of young men in white blindfolds marching in the dark, each with his hand on the shoulder of the one in front.

"No means yes," they chanted loudly and in unison. "Yes means anal." Then: "My name is Jack, I'm a necrophiliac." And more along the same lines, at the direction of older members of the fraternity they were hoping would accept them as new members.

The sudden, loud intrusion interrupted not only the peace of the Old Campus. It ended a brief detente during which there had been few such highly publicised scandals, and has reignited the recurring debate about whether American universities' fraternities and sororities should finally be banned for good after repeatedly running afoul of administrators and plaintiffs' lawyers over sexism, alcohol abuse, "hazing" (humiliating or abusive initiation rituals) and worse.

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To many foreign observers, one question is clear: why do US universities tolerate these groups?

"The number of instances of high-profile nefarious behaviour by fraternities really hasn't gone away," says James Arnold, dean of math and sciences at the College of Marin, in California, whose doctoral dissertation in higher education administration was about fraternities.

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Arnold sometimes serves as an expert witness in lawsuits brought against fraternities.

"They may have ratcheted up their public relations, but they really haven't changed their behaviour. Everything has just gone more and more underground, until something like this happens."

Following the Yale incident, the Wall Street Journal ran an op-ed proposing that fraternities be banned.

Meanwhile, women at Yale were so incensed by the incident that they complained to the federal government about an environment they called sexually hostile, and said the university failed to respond promptly to incidents of sexual harassment.

If the resulting investigation by the US Department of Education finds this to be true, Yale stands to lose some $500 million (?305 million) a year in federal funds.

But fraternities have the backing of powerful alumni on whom universities depend for contributions. The Yale fraternity Delta Kappa Epsilon (DKE), for instance, counts among its members both presidents Bush.

It was only after the government confirmed its investigation that the university announced that it would suspend the fraternity chapter from recruiting on campus or holding activities there for five years. That announcement, last month, came more than six months after the Old Campus incident. Several members of DKE were also disciplined.

DKE "threatened and intimidated others", in violation of university rules, Yale dean Mary Miller wrote in a letter to students and faculty. "Every member of our community has a legal and moral right to an educational environment free from harassment and intimidation."

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Yale, where the American fraternity system began with a debating society called Crotonia in 1738, these days tries to distance itself from its fraternities and sororities.

Tom Conroy, a Yale spokesman, points out that the fraternities are not located on university property nor authorised by the university.

He would not say how many Yale has but, according to independent sources, there are nine fraternities and seven sororities.

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Two years before the DKE episode, members of the Yale chapter of Zeta Psi photographed each other posing on the steps of the university's women's centre holding a sign that read, "We Love Yale Sluts".

Positive leadership

But some in American higher education have come to the fraternities' defence. Maravene Loeschke, president of Mansfield University, in Pennsylvania, is trying to add fraternities, something she admits seems counterintuitive "at a time when many university presidents wish, secretly or otherwise", that they could get rid of theirs.

She believes that fraternity members on her campus are serious about community service. "They have come full circle, back to what Greek life is supposed to be," Loeschke says. At Mansfield, the newest fraternity admits gay members and there are fraternities planned for black men and a sorority for black women.

"It's not a perfect world," says Loeschke, who put one fraternity on probation last year for alcohol-fuelled misdeeds. "But even that turned into a positive leadership experience," she adds. The fraternity "crafted an action plan to get their group back on track, which included refocusing on service and philanthropy and raising academic standards".

Charles Eberly, who retired last month after running a master's programme in counselling and student development at Eastern Illinois University, agrees that students in fraternities learn lessons that they can't find in a classroom - even if it is by dealing with the consequences of wrongdoing.

Supported, not chastised

The idea behind the nation's first fraternities, Eberly says, "was that students could sit down with each other and visit and learn from each other as students, which was rather revolutionary. They created something they identified as missing from their college experience."

He says fraternities ought to be supported, not chastised, by university administrators and faculty.

"I once had a student tell me that it was my job to keep him in the envelope and it was his job to get out of the envelope," says Eberly, who served as faculty adviser to a fraternity on his campus. "They have to learn how to make their way."

However, the rights of other people have to be taken into account, too, says Nicholas Syrett, a historian at the University of Northern Colorado and author of The Company He Keeps: A History of White College Fraternities.

Syrett concedes that fraternities have value, but adds: "For me the question would be, do those benefits outweigh the consequences for other students on campuses, and the answer is, no, they don't, and this incident (at Yale) was an example of that."

Women are most often victims of fraternity misbehaviour, Syrett says, and the reason is that "fraternities are interested in a certain kind of masculinity in their members, and masculinity has been defined around the idea of success with women, being able to consume a lot of alcohol, and that sort of thing."

Research by the National Institute of Justice found that fraternity men are more likely to commit sexual assaults than men who are not in fraternities.

"Fraternities, in terms of managing their public image, will always talk about the opportunities that exist for developing leadership skills," says Arnold. "And they will play up their community-service aspects, and they will say that they are not the groups that they used to be - that they do not permit or condone underage drinking or hazing.

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"But students, especially male students, are going to misbehave. Their two biggest priorities, when they're honest about it, are getting drunk and getting laid. And my opinion is that we will more than likely see things continue as usual."