At least nine of the 50 states, including California and New York, are contemplating changing or eliminating tenure laws.
Opponents of tenure tell of incompetent teachers who can't be sacked, prominent among them a high-school maths teacher cited in a speech by President Clinton. The teacher couldn't do basic algebra and let his students sleep in class, yet it cost the district $700,000 (Pounds 470,000) in legal fees to fire him.
But teachers say they need protection from arbitrary dismissal. Tenure laws date back to the harsh years of the 1920s and 1930s, when teachers became vulnerable to being sacked for political reasons.
"What you do is end up right where you were before, and that is where people are dismissed with reasons that have nothing to do with their professional qualifications," said Kathleen Lyons, spokeswoman for the National Education Association, the largest US teachers' union. "We believe (tenure) protects teachers against political and personal vendettas."
Ms Lyons tells of teachers fired for union or political organising, criticising school dress codes and failing to attend church. Tenure foes recite a litany of schools unable to purge inept employees, or forced to fight a lengthy and expensive process of appeals.
"Certainly in some situations there may be unjust dismissals, but by and large there needs to be the ability to run your organisation to achieve the best results," said Michael Latimore, director of education policy for the Minnesota Business Partnership, which is supporting proposed tenure reforms in that state. "It's just sort of a basic managerial principle."
Yet so time-consuming and expensive is it to remove a tenured teacher, he said, many districts tolerate incompetent employees in the classroom. "In effect, tenure means guaranteed employment," Mr Latimore said.
The debate is being played out before a backdrop of declining job security as major US corporations such as ATT shed workers by the tens of thousands.
"Why should taxpayers who do not have job security be paying these very high salaries to people who do?" said Myron Lieberman, an education author and researcher at Bowling Green State University in Ohio and a tenure critic.
New Republican majorities in state legislatures also are more willing to consider tenure changes than the increasingly outnumbered Democrats, who count the NEA among their closest allies.
California governor Pete Wilson, a Republican, wants tenure replaced with a system of renewable contracts. Republican New York governor George Pataki has proposed abolishing it. The Republican legislature in Wisconsin has repealed tenure for new teachers and the Republican South Dakota legislature removed from school boards the responsibility of proving "just cause" for firing a tenured teacher.
South Dakota also has extended the number of years a teacher has to work before being granted tenure; so has Pennsylvania. Virginia and Texas law-makers have proposed eliminating tenure and North Carolina is considering revoking tenure rights of teachers who work in low-performing schools.
Local teachers' unions have helped defeat attempts at changing tenure in Ohio, Michigan and Minnesota. In New York, teachers have spent $3 million on lobbying and campaign contributions, more than any other interest group; so far, tenure reform proposals there have failed. In one state, New Mexico, teachers worked with legislators dramatically to reduce the time it takes a tenured teacher to appeal against dismissal. That helped them get tenure reinstated six years after it was nullified.