A study of Washington state teachers found that deciding layoffs based solely on who has the least seniority has a significant effect on students' ability to learn.
The study comes as tens of thousands of teachers around the country stand to lose their jobs next year as federal stimulus money dries up. In most places, union contracts and other policies dictate that the least experienced teachers are the first to go.
But that comes at a price, according to the study released to the Associated Press on Thursday.
The Center for Education Data and Research at the University of Washington, which studies the relationships between education policies and student outcomes, looked at the 1,717 Washington state teachers who were given layoff notices in the last two school years.
Researchers compared the layoff notice group with a list of teachers who would have been laid off using a measurement of effectiveness known as the "value-added" system, in which teachers are judged by the improvement of their students on standardized tests.
Using teachers' past performance, the researchers predicted the performance of two hypothetical school systems: one in which the teachers receiving notices lost their jobs, and one in which more than 1,300 of the lowest-performing teachers were fired instead.
Dan Goldhaber, lead author of the study and the center's director, projected that student achievement after seniority-based layoffs would drop by an estimated 2.5 to 3.5 months of learning per student, when compared with laying off the least effective teachers.
"If your bottom line is student achievement, then this is not the best system," Goldhaber said.
But determining who are the best and worst teachers is problematic, said Randi Weingarten, president of the American Federation of Teachers, one of the country's largest teacher unions.
She criticized the research, saying it could further push school districts toward evaluating teachers strictly on student test scores. Teachers unions criticize the value-added method, pointing to research showing that it leads to inconsistent and inconclusive results.
The center's study echoes battles over teacher effectiveness in Los Angeles, where the American Civil Liberties Union sued over seniority-based layoffs, contending that it disproportionately harmed students in impoverished areas. A proposed settlement would require layoffs to occur at about the same rate campus by campus.
Goldhaber's research supported the ACLU's contention. It also found that using a seniority system requires school districts to lay off more teachers to meet their budget goals, because junior teachers earn less.