WASHINGTON — Thirteen states that enroll more than one-third of the United States' high-school students announced yesterday that they had formed a coalition to hold schools accountable for graduating students with the skills needed to succeed in college or in the workplace.

"This is the biggest step states can take to restore the value of a high-school diploma," said Ohio Gov. Bob Taft, a Republican.

The 13 states agreed to seek reforms that would raise educational standards in high school, setting math, science and language requirements that would allow students to shift smoothly into college or a demanding job. Students' progress would be tracked through testing, and schools would be held accountable for graduating all students ready for college and work.

The states in the coalition are Arkansas, Georgia, Indiana, Kentucky, Louisiana, Massachusetts, Michigan, New Jersey, Ohio, Oregon, Pennsylvania, Rhode Island and Texas.

The announcement marked the culmination of a two-day session by the National Governors Association to address what many business leaders and elected officials see as a crisis of low expectations and mediocre results in high-school education. Roughly one-third of students don't graduate on time, just as more jobs are requiring college-level skills and the nation's standing in such fields as math and science is slipping.

Education Secretary Margaret Spellings said the Bush administration endorsed the governors' call for reform and would play a supporting role following the states' lead. "Getting every child to graduate high school with a meaningful diploma in their hands is one of the biggest challenges our country faces," she told the governors.

Achieving the goals the 13 states set may not be easy. Governors will have to negotiate with school districts, state university leaders, legislators and teacher unions to craft changes that can win approval in each state.

Business leaders pledged their support for the campaign, called the American Diploma Project. It will be coordinated by Achieve Inc., a nonpartisan organization the governors created to promote education reforms. Six private foundations pledged $23 million in matching funds.

The participating states serve an estimated 5 million high-school students, or roughly 35 percent of the public-high-school population in the United States, Achieve spokesmen said.

Achieve President Michael Cohen, a former education adviser to President Clinton, said the group recruited states that seemed most serious about higher standards and poised to act. Other states are expected to join the effort soon, he said.

Bush's budget called for extending elements of his controversial No Child Left Behind law — which applies mainly to elementary and middle-school education — to high schools. It included money for additional testing at the high-school level, and a $1.24 billion initiative aimed at helping students who are falling behind or are in danger of dropping out.

The governors did not take a position on Bush's proposals. Congress will rework several major federal education laws this year, and the governors asked Washington to reduce paperwork requirements, grant them greater authority over the uses of federal money and support efforts to redesign high schools.