Since 2009, Utah has used computers to grade essays on a state student-assessment test. And testing companies use essay-evaluating software as one of two graders on graduate-school admissions exams such as the GRE. But how well, really, can a computer grade an essay?

To find out, Mark Shermis, an education researcher at the University of Akron, ran 22,029 standardized middle- and high-school essays through software from eight companies (plus one open-source algorithm). The programs, which generally track content, organization and style, generated results indistinguishable from those of humans—just much faster. With that kind of efficiency, robot graders could mean more homework for students everywhere.