The largest U.S. teachers union called for requiring students to earn a high school diploma or stay in school until age 21.

The National Education Association made the proposal as part of $1 billion-a-year plan it offered this week to increase high school graduation rates. In March, a Gates Foundation study found that a third of all public high school students fail to graduate and more than 80 percent of the nation's 3.5 million dropouts ages 16 to 25 regretted their decision.

"This is no longer about students slipping through the cracks of the education system," said Reg Weaver, president of the 3.2 million-member National Education Association. "Those cracks are now craters."

Congress has been reluctant to fund previous proposals to improve education. One initiative languishing on Capitol Hill would provide $10 billion a year for research-related tax breaks and scholarships for math and science students. The proposal was backed by President Bush and lawmakers from both parties.

The NEA said its plan, costing an estimated $10 billion over 10 years, would establish "high school graduation centers for students 19 to 21 years old to provide specialized instruction and counseling" apart from younger students.

In proposing to raise the mandatory age of attendance, the NEA cited a 1991 study by researchers at Harvard University and the Massachusetts Institute of Technology that credited mandatory schooling laws with keeping about 25 percent of potential dropouts in school.

"Just as we established compulsory attendance at the age of 16 or 17 in the beginning of the 20th century, it is appropriate to eradicate the idea of dropping out before you achieve a diploma," Weaver said.

In presenting the plan, Weaver was joined by Rep. Ruben Hinojosa, a Democrat from Texas, who proposed a measure last year that would spend $1 billion on dropout initiatives, and Kathryn Brown, senior vice president of Verizon.

Verizon, based in New York and one of the largest U.S. telephone companies, can't find enough people capable of handling customer inquiries by sitting in front of multiple computer screens and interpreting their records, Brown said.

'HIGH SCHOOL SKILLS'

"Those are high school skills, and yet we're having difficulty doing that," she said.

The Gates Foundation study of nearly 500 former students nationwide found the most common reason for leaving, cited by 47 percent, was that their classes "weren't interesting." Eighty-eight percent reported having passing grades, and 70 percent said they could have graduated if they had tried, the survey said.

Those who considered returning to school often "don't think that anybody wants them to come back," Weaver said. "And if in fact they do want to come back, they don't know where to come back to."

The nation's other major teacher union, the 1.3 million-member American Federation of Teachers, supports the concepts of the NEA plan, without being able to comment on specific details, AFT spokeswoman Leslie Getzinger said.

EARNINGS OVER LIFETIME

One way to persuade students to complete high school is to make them aware of data that shows high school graduates earn more than $1 million over their lifetimes, while dropouts earn only about $600,000, said Edward DeJesus, president of the Youth Development and Research Fund in Gaithersburg, Maryland.

Over four years of high school, that translates into about $500 to $700 a day, DeJesus said.

Congress also needs to change the No Child Left Behind law so that schools trying to meet minimum testing standards do not force out low-performing students, said John Bridgeland, a former White House policy adviser in the Bush administration.