Ariana Contreras is the first in her family to attend, and graduate from, college. In a few days, she will receive her bachelor’s degree in biological science on my campus, UC Riverside, and plans to seek a master’s in environmental science. She grew up in Colton, roughly 15 minutes from campus.

Contreras represents an amazing and continuing shift in the makeup of the University of California’s student population. For the first time across system, Latinos surpassed whites for freshman admission offers this spring, with 28.8 percent admitted to at least one UC campus, compared with 26.8 percent for whites.

Unfortunately, this rising diversity is not reflected in graduation rates. According to the most recent Department of Education statistics, 69 percent of Asian American and 62 percent of white students had earned a degree six years after enrolling, a widely accepted standard in measuring academic success. But only 50 percent of Latinos and 40 percent of African Americans did so.

The challenge of boosting these graduation rates will largely fall on public colleges and universities, which enroll 72 percent of postsecondary students.

The traditional sink-or-swim approach, all too common at money-strapped public institutions, will not increase the graduation rates of this diverse body of students, whatever their aptitude and experience. What’s needed is an institution-wide push to provide programs that can prevent struggling students from falling between the cracks and leaving school.

About 12 years ago, administrators and faculty at UC Riverside recognized that our students were different from the traditional UC student. Many were the first in their families to attend college. Others were from low-income families or graduates of poorly performing high schools. The racial and ethnic mix on our campus was the most diverse in the UC system.

These students faced many barriers to completing their college work. Some were not adequately academically prepared. Others worried that family finances might force them at any time to drop out for a quarter or longer.

To help these students realize their dreams of earning a college degree, we adopted an activist approach along three fronts.

First, we created learning communities, overseen by faculty and academic staff, of students — usually 20 to 30 freshmen and sophomores — taking the same coursework. Study groups were formed to assist students in developing scholarly habits, interacting with their peers on campus and discovering career opportunities. About 1,900 students participate each year.

Second, courses associated with high rates of poor student performance — biology, chemistry, math, psychology, economics — were identified and supplemental instruction, conducted by professors and teaching assistants, was offered to help struggling students.

Finally, an early warning system was set up to identify students at risk of failing. Once identified, advisers encouraged them to take the available supplemental instruction.

The result? Rough parity in graduation rates among the racial and ethnic groups on our campus. According to the most recent data, 70 percent of our African American students in the entering 2007 freshmen class had earned their degrees six years later, compared to 63 percent of whites. And the Latino graduation rate was only a percentage point behind whites.

Other public universities are also taking an aggressive approach to ensuring that all their students have an equal chance to graduate. Georgia State University has invested in supplemental instruction, first-year learning communities, and other programs. Arizona State University has adopted a sophisticated data system that helps students know they are on track.

The bittersweet news highlights the difficult mission public colleges and universities face: increasing student graduation rates while simultaneously maximizing access to — and diversity on — our campuses.

The problem is that our public institutions tend to applaud the rising diversity on their campuses and then step back and let students fend for themselves. But nothing less than a bold, hands-on approach to educating this new generation of students will allow us to fulfill our mission to graduate all of America.

Kim A. Wilcox is Chancellor of the University of California, Riverside.