U.S. Education Secretary Arne Duncan was in St. Louis last week with Randi Weingarten, president of American Federation of Teachers, to visit city public schools. At a joint appearance at Lexington School, the secretary was happy to cede the spotlight to Ms. Weingarten. Here's why:

The Obama administration's highest-profile education initiative is called the "Race to the Top Fund." It's a grant program in which states are competing for $4.3 billion to help turn around troubled districts, promote the use of international education benchmarks, advance teacher professionalism and develop data systems that measure teacher and student performance.

The National Education Association, the nation's largest teachers union, has criticized the program.

The NEA says the initiative has an "unhealthy focus on standardized tests" and argues that "it is inappropriate to require that states be able to link data on student achievement to individual teachers for the purpose of teacher and principal evaluation."

The program encourages the creation of "high-quality charter schools," which the NEA sees as proof that "the administration has decided that charter schools are the only answer to what ails America's public schools."

Ms. Weingarten, on behalf of the AFT, took a different tack and tone.

She described a charter school in New York City — the Green Dot School — in which teachers recently entered into "a very different kind of contract, a contract that was based on what the school and the kids needed."

"There's not a start time and an end time; there's a professional day in which teachers have certain responsibilities," she said. "There's also, instead of tenure, a 'just cause' dismissal standard for everyone. We've created a sense that you do your work, you get help when you need it, but if you're not working out, you are going to be separated from service — yes, of course, in a fair process, but separated from service."

In exchange, Green Dot teachers receive 15 percent higher pay than teachers in the New York City school district and a lower teacher-student ratio.

"Just the way charter schools can be incubators for great instructional plans, they can be incubators for great labor relations plans," she said.

Efforts to boost student achievement in troubled districts, even when backed by billions of dollars, depend on teachers. But teachers unions often are seen, with some justification, as narrowly focused on protecting jobs of teachers accused of poor performance. This perception pushes parents already frustrated with traditional public schools to seek alternatives — undermining the security of the majority of teachers who do their jobs well.

Teachers can turn that perception around. The St. Louis Public Schools and the union representing its teachers recently took an important step in that direction by agreeing to flexible work- days and conditions for teachers and principals at five pilot schools launched at the start of this school year.

In competition over what kinds of schools best serve struggling districts, professionalism is the card that teachers can play to win students, security and a major role in school reform.