“Let’s face the realities of automatic essay scoring,” the group’s statement reads in part. “Computers cannot ‘read.’ They cannot measure the essentials of effective written communication: accuracy, reasoning, adequacy of evidence, good sense, ethical stance, convincing argument, meaningful organization, clarity, and veracity, among others.”

But EdX expects its software to be adopted widely by schools and universities. EdX offers free online classes from Harvard, M.I.T. and the University of California, Berkeley; this fall, it will add classes from Wellesley, Georgetown and the University of Texas. In all, 12 universities participate in EdX, which offers certificates for course completion and has said that it plans to continue to expand next year, including adding international schools.

The EdX assessment tool requires human teachers, or graders, to first grade 100 essays or essay questions. The system then uses a variety of machine-learning techniques to train itself to be able to grade any number of essays or answers automatically and almost instantaneously.

The software will assign a grade depending on the scoring system created by the teacher, whether it is a letter grade or numerical rank. It will also provide general feedback, like telling a student whether an answer was on topic or not.

Dr. Agarwal said he believed that the software was nearing the capability of human grading.

“This is machine learning and there is a long way to go, but it’s good enough and the upside is huge,” he said. “We found that the quality of the grading is similar to the variation you find from instructor to instructor.”

EdX is not the first to use automated assessment technology, which dates to early mainframe computers in the 1960s. There is now a range of companies offering commercial programs to grade written test answers, and four states — Louisiana, North Dakota, Utah and West Virginia — are using some form of the technology in secondary schools. A fifth, Indiana, has experimented with it. In some cases the software is used as a “second reader,” to check the reliability of the human graders.

But the growing influence of the EdX consortium to set standards is likely to give the technology a boost. On Tuesday, Stanford announced that it would work with EdX to develop a joint educational system that will incorporate the automated assessment technology.