Published in the Wall Street Journal (Aug. 28 online and Aug. 29 print edition)

‘Crowd-sourcing’ the grading of an essay online is no substitute for thoughtful evaluation by a trained educator.

As classes resume on our nation’s campuses, amid anxiety about high tuition, student debt and other concerns, it’s worth examining what we value in college education. The question warrants consideration, in particular, following a recent recommendation by distinguished economists, appointed by the National Academy of Sciences, proposing to define the “output” of higher education as a combination of credit hours awarded and degrees earned.

That reduces the work of colleges to counting how many students they push through the system—a bit like defining a movie studio’s output as the number of feet of raw footage shot, with no consideration of whether the resulting movies are any good.

Most of us in higher education take the long view about the value of what we do. Sure, students graduate with plenty of facts in their heads. But the transmission of information is merely the starting point, a critical tool through which we engage the higher faculties of the mind.

What really matters is the set of deeper abilities—to write effectively, argue persuasively, solve problems creatively, adapt and learn independently—that students develop while in college and use for the rest of their lives.

At Williams College, where I work, we’ve analyzed which educational inputs best predict progress in these deeper aspects of student learning. The answer is unambiguous: By far, the factor that correlates most highly with gains in these skills is the amount of personal contact a student has with professors. Not virtual contact, but interaction with real, live human beings, whether in the classroom, or in faculty offices, or in the dining halls. Nothing else—not the details of the curriculum, not the choice of major, not the student’s GPA—predicts self-reported gains in these critical capacities nearly as well as how much time a student spent with professors.

What follows from this finding is obvious, but apparently in need of saying these days: What we do is expensive—and worth it—because these rich, human interactions can’t be replaced by any magical application of technology.

Technology has and will continue to improve how we teach. But what it cannot do is remove human beings from the equation. Coursera, one of the new purveyors of massive, open online courses, proposes to crowd-source the grading of essays, as if averaging letter grades assigned by five random peers were the educational equivalent of a highly trained professor providing thoughtful evaluation and detailed response. To pretend that this is so is to deny the most significant purposes of education, and to forfeit its true value.

It follows that standard economic models that define productivity as total output per unit of labor are ill-suited to analyzing the activities of colleges. Understandable concerns about the cost of college have spawned a spate of high-stakes considerations of productivity; in Texas, “low-productivity” programs at flagship universities have been targeted for elimination. Yet the only way to achieve higher productivity, as the National Academy would define it, is to reduce each student’s time with the faculty. We know that while such approaches may allow us to deliver some facts to some students more efficiently in the short run, the approaches will undermine the fundamental purpose of education in the long run.

Equally misguided is the common practice of judging a school’s success by measuring the net worth of its alumni. Is a Williams graduate who is teaching elementary school less successful, less influential, less transformed than she would be if she had become a banker? There’s no reason to think so, and anyone assessing colleges or setting public policy on that assumption is being mischievous.

Education is not a commodity. It’s a social process, and its value, including its economic value, both to the graduate and to society is unquestionable. It is equally true that this value cannot be reduced to a single number, however much the measurers of productivity—or those who rank us in magazines—may wish it otherwise.

Mr. Falk is president of and professor of physics at Williams College.

Copyright 2012 Dow Jones & Company, Inc. All Rights Reserved