If you're lucky, your boss has made it clear to you what it means to do a good job — and rewards you just as clearly for doing it. Teachers aren't so lucky.
First, how do you measure good teaching? How about student test scores? Teachers — and their unions — will tell you that test scores show only part of the picture.
The National Education Association, which represents most of America's teachers, states, "Just as a standardized test is not an accurate reflection of what a student knows, it is not an accurate reflection of what a teacher has taught."
Teachers ask, how can they be held responsible when so much that influences a child's school performance is out of their control — whether the child got a good night's sleep (indeed, whether the child had a place to sleep at all), whether the student had breakfast, or is encouraged to do homework, or is living in a household under stress.
And what about teachers who teach subjects that aren't tested, like technology, art, science electives, and so on?
George Jackson, spokesman for the American Federation of Teachers union, said, "We want to make sure [compensation programs] are fair for all teachers, and that all teachers get a chance to participate."
So, if teachers can't be paid to do better, based on how their students perform, how is their performance to be measured?
Some early experiments with merit pay let principals decide who should earn a bonus, and based on what criteria. Opponents say that's too subjective, and it may reward compliance with a principal's rules more than how well teachers educate children.
A deeper concern for teachers and their unions is that simple, test-based merit pay instruments will force teachers to compete to get the "best" students in their classes, or worse, give them incentives to help students to cheat on the tests that will determine their pay.
Teachers say they get better if they help each other, not compete with each other.
What would happen if a teacher withheld some useful teaching tool, Web site, approach, or knowledge about a student, in order to improve his or her chances of being among the few to earn rewards? To the extent that merit pay undermines teamwork, it undermines teaching, they say.
The powerful National Education Association has held a firm line against salary systems based on teacher performance, preferring the traditional system that ties pay to experience and advanced study. They say those factors are most closely linked to good teaching.
But the American Federation of Teachers has been more supportive of local experiments, as long as teachers are included in their design.
"We take a very careful look at the level of collaboration that teachers have in creating these plans," said Jackson. He added that professional supports — mentoring and teacher development — are as important as the money that goes with it.
Florida legislators were shocked last year when few teachers agreed to compete for incentive pay, tied to student test performance. The plan's prospects have improved, since lawmakers redesigned the program to lessen the importance of test scores, and to allow teams of teachers, rather than just individual teachers, to quality.
A growing number of local unions have agreed to experiment with alternative pay structures, especially to encourage teachers to move to low-performing schools or to teach high-needs subjects, like math and science.
Promising programs are underway in Denver, Chicago, Austin, and Minneapolis, among others. Many distribute bonuses throughout the school — even janitors and lunch ladies can qualify.
And the pot of money is growing.
Since last November, the U.S. Department of Education has awarded 33 grants to pay out more than $477 million over the next five years. That money will go toward teacher incentives that improve student achievement, and close achievement gaps in high-poverty schools. Many millions more in private funds have also been distributed.
Above all, teacher unions have resisted merit pay in order to keep the focus on their top concern — the need to raise the floor on low teacher salaries.
"If you're not paying teachers a competitive salary to begin with," Jackson said, "then, any professional compensation plan that you come up with on top of that is not addressing the need to get the best teachers in, doing the best work that they can do."
The unions may have to take on the merit pay battle first, though.
Congress is moving to include a measure calling for performance pay and teacher evaluations, based on standardized test scores, in the reauthorization of the No Child Left Behind law being negotiated in Washington right now.