Abolishing tuition at public universities has become a hot topic on the campaign trail, with many Democratic presidential candidates endorsing the idea. But if access to college is the issue, two other barriers could be addressed far more quickly and cheaply: convincing high-achieving high school seniors to apply for available grant money and persuading those who have been accepted to college to enroll.

These two factors have been estimated to keep several hundred thousand high school graduates from going to college every year. Not surprisingly, "new gen" students — those from low-income families and underrepresented minority groups and students who are the first in their family to go to college — are the hardest hit. The good news is that low-cost "nudges" can help these students get to and through college.

The sticker price of higher education unnerves many high-achieving, new-gen students. Federal and state financial aid can ease the burden, but every year thousands of them who would likely qualify don't apply. High school counselors, who could show them the ropes, are often overwhelmed by their caseloads.

Without the kind of hand-holding affluent youth take for granted, many new-gen students have a hard time figuring how to secure the financial aid they are entitled to. Meanwhile, students who need the money less but know how to work the system get more of it.

California's Cal Grant program, designed to help level the financial playing field, recently took a simple step to help change that. Researchers from the California Policy Lab, a joint UC Berkeley-UCLA project, were invited by the California Student Aid Commission to rewrite a letter sent out by the commission explaining the application process. They made common-sense changes, shortening the letter considerably and removing jargon.

This change, which cost nothing, had a small but significant effect: 67.6% of the students who received the simplified letter signed up, compared with 62% of those who got the standard letter.

The positive effect on applications would probably be even bigger if the Student Aid Commission switched to texts from old-fashioned mail. Texts are how millennials communicate: They spend three times more time texting than calling or emailing and almost no time reading and writing letters. Why not connect with them on their go-to devices?

In addition to streamlining the prose of the aid commission's letter, the researchers tested another approach backed by social psychology research. Many new-gen students harbor doubts that they can make it, and reassuring them that they are college material can help to dispel those fears. The researchers added two boldface sentences to the letter: "You have shown that you're the kind of person who belongs in college. We've been working hard to help you get there!" Simply adding those words increased the number of applicants by 2.5%.

Another issue ripe for nudges is so-called "summer melt." About 10% to 20% of students accepted by a college inform the institution they are coming, pay a deposit, but never show up. Some students decide not to enroll because of a change of heart; they decide college is not for them, or a change of circumstances keeps them tethered to their families. But the explanation is often a lack of knowledge on the part of students about what they need to do once they are accepted.

At some universities, the road from application to registration feels like a Kafkaesque journey, with hard-to-decipher instructions regarding how to submit final-semester high school grades, register for freshman orientation, sign up for classes and receive financial aid. New-gen students are the most likely to find the process daunting.

Summer melt plagued Georgia State University, a national pioneer in removing roadblocks to graduation, and the university was determined to solve the problem. Taking advantage of students' reliance on cell phones, GSU made clever use of an artificial intelligence-enhanced chatbot called Pounce. If a prospective student hadn't submitted something the university needed — say, a financial aid form — Pounce reminded them of the deadline and offered immediate responses to their questions.

In the past, GSU advisers had their hands full answering routine questions. This high-tech approach freed them to concentrate on the kind of student concerns that actually require a human touch. The chatbot enabled the university to reduce summer melt by more than a third. That translated into about 600 more freshmen.

The takeaway from the Cal Grant letter and summer melt stories is much the same. Showing students they belong and that the institution is committed to their success can make a world of difference. What's more, the same strategies that expand college access can be adapted to nudge students into completing their degree. With a scandalously high 40% of undergraduates dropping out, that's a lesson universities need to learn.

David L. Kirp is a professor of public policy at the University of California Berkeley and is the author of "The College Dropout Scandal."