The writer, who is on leave as a high school teacher in Los Angeles, is a member of United Teachers Los Angeles and executive director of Teachers for a New Unionism.

We have all heard about the dramatic changes in the American electorate and how, because he spoke to the concerns of the growing numbers of Hispanic, black, female and younger voters, President Obama was reelected despite adverse economic conditions.

Another critical demographic shift is occurring. This one is taking place, quietly, in teachers unions: Over the past several years, teachers who have spent 10 years or fewer in the classroom have become the dues-paying majority. The impact of this new majority is as important to the role of unions as the changing electorate is to presidential elections. These newer teachers, along with many longtime teachers, are looking for their unions to elevate the profession — not to sacrifice teaching quality for job security.

But the word is definitely not out. I’m a teacher and a union member — and a member of the new majority. Not long after the Chicago teachers strike ended, I had dinner with lifelong Democrats. Instead of support for a revitalized union movement or sympathy for the plight of teachers, the conversation included such comments as: “The last thing teachers unions think about are students,” “Teachers unions haven’t addressed teacher-quality issues, especially with the weakest teachers” and “Teachers unions have to start focusing on something other than pay and tenure.”

It was painful to hear this — especially because such sentiments accurately describe the situation in many large urban teachers unions. In smaller unions across the country, however, progressive teachers are committed to meeting student needs and advancing the profession. And the new majority is accelerating those changes.

The leaders of the biggest teachers unions, including in New York City, Chicago and Los Angeles, largely focus on narrow contractual protections to the detriment of teacher quality and student achievement, issues that are of critical concern to the new majority of teachers.

Unions in small and medium-size districts are taking a different approach. Eschewing top-down leadership, these unions are highly collaborative. As a result, their actions reflect their members’ priorities: improved student achievement and upgraded teacher quality.

At Green Dot Public Schools in Los Angeles, the union’s mission sets out that “every student deserves to be taught by an effective teacher.” The union reached a membership-ratified agreement last spring with management on a rigorous evaluation system that includes test data as 25 percent of a teacher’s total evaluation score.

In Connecticut, the New Haven Federation of Teachers abandoned its traditionally adversarial role and collaborated with both the school district and the mayor’s office to develop and implement an evaluation system that relies heavily on evidence of student progress — including the use of standardized tests and other measures. The new system, which is strongly supported by New Haven’s 1,600 unionized teachers, more effectively supports struggling teachers and identifies unacceptable performers and helps transition them out of the system.

In Maryland, the Montgomery County Education Association participates in a Peer Assistance and Review program that helps mentor new teachers and struggling veterans. It’s a program with real teeth: A panel composed equally of teachers and administrators has the power to remove teachers who fail to improve with mentoring.

Members of the Newark Teachers Union recently approved a contract tying teacher salaries to measures of effectiveness and giving teachers a leading role in establishing and monitoring those measures.

This encouraging transformation extends beyond small and medium-size districts. Increasingly, statewide teacher associations are collaboratively addressing teacher-quality and student achievement issues. In June, the Massachusetts Teachers Association supported statewide legislation requiring that teacher performance be a major factor in staffing and personnel decisions.

Signs of change are appearing in major urban unions. In New York, Boston and Los Angeles, teachers voice groups — representing the opinions of the new majority as well as those of many senior teachers — have become strong advocates for changes affecting teacher quality. Their efforts, combined with those of civil rights organizations calling for more attention to student achievement, and forces within the Democratic Party pushing for accountability, are putting tremendous pressure on entrenched leadership to adopt more responsive, democratic policies. Transformation of major teachers unions may happen in the near future.

The democratic system is at the heart of our unions’ governance. The majority of teachers believe that student achievement comes first. It’s only a matter of time until all teachers unions reflect that belief — and ardently work to support it.