WASHINGTON – Hundreds of thousands of high school dropouts hoping to earn equivalency diplomas will have to pass a more challenging GED test that is being designed to improve the prospects of low-skilled workers in a high-tech economy.

The largest overhaul in the exam’s 70-year history follows growing criticism that it has fallen far short of its promise to offer a second chance for the 39 million adult Americans without high school diplomas. Very few of those who pass the GED test pursue higher education, and most struggle to earn a living wage.

The new exam, scheduled to be introduced in January, will emphasize skills that are more relevant to today’s employers and colleges, including critical thinking and basic computer literacy as the test goes digital and the pencil-and-paper version is abandoned. It also will be aligned to national academic standards approved by 45 states and the District of Columbia, matching it more closely to the education students are now expected to receive in public schools.

C.T. Turner, a spokesman for the GED Testing Service, said the new test is motivated by the economic reality that a GED alone, like a high school diploma, will not help the approximately 800,000 people who take the test each year. The test has to become a “steppingstone” to college, he said.

“If we are not going to give them a chance to better their lives, we are giving them false hope,” he said. “We are assigning them to a dead-end job.”

The United States has slipped from first in the world to 16th in college attainment for young adults, a trend that President Barack Obama has pledged to reverse.

The battery of tests known as the GED, for General Educational Development, was first administered in the 1940s to give returning World War II veterans a way to return to school and take advantage of the GI Bill. It expanded as federal funding began flowing to adult education programs and GED programs were introduced in prisons.

The test has increased in rigor four times. Today’s challenge – to prepare high school dropouts for college – is steep, particularly given that many preparation programs squeeze four years of high school material into crash courses offered in church basements, said Terry Grobe, a program director for Boston-based Jobs for the Future.

More than 20 people crammed into a narrow classroom on an April morning at the Woodbridge Workforce Center for the first day of a 12-week GED preparation course.

Some students at the center in Woodbridge, Va. hope the GED will help them move into management at McDonald’s or the Calvin Klein store at the mall. Most have more distant goals: to stop cleaning office buildings or working the split shift as a bus driver and to become an X-ray technician or a preschool teacher.

“I am here today because I want to go to college,” said Judy James, 41, of Woodbridge, who left high school when she had her first child, who is now enrolled in college.

The average GED test taker is 26 years old, and nearly a quarter of all test takers are 16 to 18.

A 40-week program run by the nonprofit Living Classrooms in the District of Columbia serves 20 teenagers from the region who were released from juvenile detention. The program offers test preparation along with training in woodworking and metal shop and basic life skills.

Toni Lemons, program director, said 40 weeks is sometimes not long enough. Many arrive with third- or fourth-grade-level skills, and some are not ready for the test by the end of the program.

A 2011 study by the GED Testing Service found that although about 60 percent of test takers said they planned to pursue postsecondary education, just 43 percent enrolled. Of those who went on, about a third dropped out after a single semester and only 12 percent graduated.

Without further schooling, the GED offers little economic payoff. Nobel Prize-winning economist James Heckman found in the early 1990s that America’s high school equivalency certificate was not equivalent in the labor market. Those who passed the GED earned far less than high school graduates and worked fewer hours.

On average, GED recipients fared about the same as dropouts who never took the test, further research showed. One subgroup, the lowest-skilled test takers, did eventually earn bigger paychecks, but not enough to lift them out of poverty.

Heckman and other economists have concluded that the GED test is limited in its ability to predict success because it only measures cognitive ability.

“There are other skills that matter in life: showing up in class, doing your homework, getting along with peers – things that matter in school and in college,” said John Eric Humphries, a University of Chicago economist. Such skills are more difficult to measure and more likely to be developed in school, he said.

But Turner said that by setting a higher bar with the tougher test, more people will be prepared to enter college without getting stuck in remedial courses, a common reason students drop out.

The new seven-hour exam will condense five subject-area subtests to four: Reasoning through Language Arts; Math; Science; and Social Studies. The test will require more analysis and a deeper understanding of mathematics. Instead of one essay, there will be two written response sections.

The threshold for passing the new test, like the current one, will be based on how a random sample of graduating high school seniors perform on it. The cut score is set so that about 40 percent of traditional high school students could not pass all five subtests.

More than just providing a number score, the updated assessments will come with a detailed score card that lists which skills the test takers have mastered and which are still lacking, indicating whether they have enough grounding in algebra to qualify for a workforce training program, for example, or whether they are prepared to enroll in credit-bearing college classes.

The new test will cost $120 per student, more than double its current cost in some states.