A requirement that Yale undergraduates on financial aid pay up to $6,400 annually toward their education is coming under protest from students who argue it creates a divide along class lines and keeps them from participating more in campus life.

A petition drive has gathered signatures from more than a thousand students calling for the elimination of the student contribution.

The Ivy League university with a $23.9 billion endowment has some of the nation's most generous aid policies, including a promise that students can graduate without any loans, but some students say they have been advised to borrow money when they had trouble meeting the financial obligation.

Cristobal Trujillo, a 3rd year student, said he struggles to meet the requirement despite working eight to 12 hours a week at the school library.

"For me, it's been kind of stressful to be in the situation of having to give up my time, and seeing other people do extracurriculars, go to office hours," he said.

University spokeswoman Karen Peart said Yale, like all schools, "expects students to make a modest contribution to their education."

Ronald Ehrenberg, president of the Cornell Higher Education Research Institute, said Yale is among a tiny number of universities that have the resources to set any aid policies they like, but school officials may believe in principle that students should contribute.

"Should students of limited means be expected to contribute to their education through working? That's not a question I can answer. I have my own views," he said. "Any student who gets to go to Yale is both very talented and very, very lucky."

The cost to attend Yale annually is $63,250 and the university says more than half of students receive need-based aid, with scholarship grants averaging $41,250. The minimum wage for campus jobs is $12 an hour at Yale, which has 5,380 undergraduate students.

The student contribution, which includes money expected to be earned during the school year and the summer, is $6,400 for upperclassmen and slightly less for freshmen.

The amount has been rising steadily in recent years, according to Avani Mehta, a leader of the Students Unite Now group that organized a demonstration last week to deliver the petition to Yale's president. Mehta said the requirement creates a divide that also breaks down along racial lines.