Paris — Calling the community-college system in the United States “one of America’s best-kept secrets,” Jill Biden highlighted the virtues of an often overlooked sector of American higher education in a speech here today at an international conference of Unesco, the United Nations’ education-and-science agency.

The vice president’s wife, who has long taught at community colleges and currently serves as an adjunct professor of English at Northern Virginia Community College, told delegates to the 2009 World Conference on Higher Education that community colleges are of vital importance to President Obama’s goal of the United States’ having the highest proportion of college graduates in the world by 2020.

American universities are often cited as models of global excellence, but international attention is usually on elite research institutions, and the role community colleges play is neglected. In a time of economic crisis, that role is becoming increasingly important, Ms. Biden said. “More and more often in these difficult financial times, community colleges are an affordable way for students from middle-class families to complete the first two years of a baccalaureate degree before moving on to a four-year university,” she said.

Community colleges have for the past three decades been the fastest-growing sector in American higher education, Ms. Biden said, and the country’s 1,200 community colleges account for nearly half of all American undergraduates. A class she taught last year to a group that included students from 22 countries illustrates the essential role these locally focused institutions play in integrating recent immigrants — who have in many cases obtained degrees in their home countries — into their communities. —Aisha Labi