The big defenders of seniority-based layoffs are, not surprisingly, the teachers unions. Seniority is a common tool for ensuring that layoffs aren't arbitrary, and that those who have put in the most time have the most job protection.
But even unions say they'd be open to other systems – once credible evaluations exist. In the absence of those, they believe that seniority is not only the most impartial way to conduct layoffs, but also gives weight to classroom experience.
"Experience does have value," says Rob Weil, director of field programs and educational issues for the American Federation of Teachers (AFT). "Is it a complete proxy for teacher quality? No. But it's the best we have as we move forward to get a better system."
Mr. Weil and others worry that more experienced – and more highly paid – teachers will be more vulnerable without protections.