ASHLAND, Va. — Each incoming freshman at Randolph-Macon College this year was eligible to take part in a brief signing ceremony.

The new student, along with a parent and the college president, could sign a special agreement that is emerging at some colleges and universities: As long as the student keeps up with academic work and meets regularly with advisers, the college guarantees that earning a degree there will take no more than four years.

If it fails to hold up its end of the bargain — if required classes are not available, or if advisers give poor counsel — the college promises to cover the cost of additional tuition until the degree is completed.

Four-year degree guarantees, as they have become known, are being offered at a growing number of smaller private colleges. They work as a marketing tool, giving colleges a way to ease parents’ fears that their children might enjoy college enough to stick around for five or six costly years. And they help to focus attention on the task at hand: graduating in four years.