But as the conference opened, that view was under challenge in a number of state capitals.
Republicans in several states have proposed legislation in recent weeks that would bar teachers’ unions from all policy discussions, except when the time comes to negotiate compensation. In Tennessee and Wisconsin, Republicans have proposed stripping teachers’ unions of collective bargaining rights altogether.
Education historians said the unions were facing the harshest political climate since states began extending legal bargaining rights to schoolteachers decades ago.
The conference, convened by the Department of Education, drew school authorities and teachers’ union leaders from 150 districts across the nation to Denver to discuss ways of working together. To participate, each district’s superintendent, school board president and teachers’ union leader had to sign a pledge to collaborate in good faith to raise student achievement.
Some districts that had hoped to participate could not because relations grew too hostile before the conference.
They included New York, where the schools chancellor, Cathleen P. Black, and the United Federation of Teachers president, Michael Mulgrew, had each signed the pledge. But recent criticism by Ms. Black of the city’s system of seniority-based teacher layoffs angered Mr. Mulgrew, he said, and late last week he pulled out of the conference.
“I wasn’t going to walk into Denver with the chancellor and say, ‘We’re the hypocrites, here for the conference,’ ” Mr. Mulgrew said.
Natalie Ravitz, a spokeswoman for Ms. Black, said the chancellor was disappointed. “We think there are critical issues we need to work together on,” Ms. Ravitz said.
Chicago, Miami-Dade, Philadelphia and eight others among the nation’s 25 largest school systems were at the conference, alongside representatives of 140 smaller districts from 40 states.
In his opening remarks at the conference, called Advancing Student Achievement Through Labor-Management Collaboration, Mr. Duncan commended several districts and their unions.
Among them were Douglas County near Denver, where, he said, the union helped the district pioneer a new teacher evaluation system. In New Haven, a union contract established an innovative mentoring program. And in Los Angeles, the union contract at the Green Dot charter school network details teachers’ instructional responsibilities rather than their working hours.
The conference comes at a time when thousands of districts are facing their most severe budget cuts in a generation, and union contracts calling for layoffs based on seniority could force many districts to dismiss their most energetic young teachers.
But changing these policies could also prompt some districts to remove more experienced, higher paid teachers to balance their budgets.
Mr. Duncan urged participants to search for solutions to the dilemmas posed by mass teacher layoffs.
“We have to learn to problem-solve together,” he said, underscoring his view that school systems can face challenges most effectively by working with the unions.
But in some states an alternate view appeared to be gaining force.
The Idaho schools superintendent, Tom Luna, a Republican, has proposed legislation that would limit collective bargaining to teacher compensation, and exclude unions from deliberations over the design of education policies. Republican lawmakers in Indiana have proposed similar legislation.
Gov. Scott Walker of Wisconsin has gone further, proposing to end collective bargaining rights for nearly all the state’s 175,000 public sector workers, more than half of whom are teachers. That proposal could pass since Republicans command large majorities in the Legislature.
In Tennessee, State Representative Debra Young Maggart, the chairwoman of the Republican caucus, also introduced legislation that would bar teachers’ unions from collective bargaining.
“Teachers’ unions have been blocking education reform, and my bill will deal with the problem,” Ms. Maggart said.
But Sharon Vandagriff, president of the teachers’ union in Hamilton County, Tenn., who came to Denver for the conference, said her union had worked for years with school authorities to overhaul struggling schools in Chattanooga. Across Tennessee, unions made concessions that paved the way last year for the state to win $500 million in federal Race to the Top money, she said, adding that Ms. Maggart’s bill has demoralized many teachers.
“It feels like an attack,” she said.
Some Democrats, too, are adopting a tougher stance toward teachers’ unions.
“We think they have a right to exist and a role to play in education reform,” said Joe Williams, executive director of Democrats for Education Reform, an advocacy group that pushes for charter schools. “But we wish management would be more aggressive. When management tries to appease, we end up with contracts that aren’t good for public education.”
Charles Taylor Kerchner, a professor of education at Claremont Graduate University who studies labor union history, said, “This is the harshest time for teachers’ unions that I’ve seen since the advent of legislatively sanctioned collective bargaining half a century ago.”
