On Tuesday, President Obama reaffirmed his commitment to improving education and renewed his call to expand the use of merit pay as an incentive for excellent teaching. Pay for performance is an idea whose time has come. The venerable "step system" for determining salaries is an artifact of the past that's rife with inequities and, since rewards are based primarily on years of service not outcomes, a poor motivational tool. Creating and implementing a fair and successful system that teachers support won't be easy, but it must be done.

Teacher salaries vary enormously from district to district, in good measure because communities differ drastically in property wealth. But pay in many districts, Concord included, ranges from respectable to excellent. With that pay should come more accountability than currently exists.

Systems used to compensate teachers - and administrators - should more closely mirror those in the workplaces of other professionals, which is to say they should be based in fair measure on performance. An increasing number of school districts are experimenting with merit pay to one extent or another. Concord should do so as well.

The experiments with merit pay have taken two basic forms. In the first and most common, little or no change is made in the step system, and merit pay is given in the form of bonuses. In the second, now in use in Denver, Colo., a merit pay system replaces the traditional step system.

In the more familiar merit system, bonuses are typically dispensed to individuals whose performance has been rated superior - or distributed school-wide when a given goal is met.

One challenged Little Rock, Ark., elementary school offered school-wide bonuses if student test scores improved. Tests alone are a poor measure of educator effectiveness, but the offer sparked some interesting developments. Cafeteria workers began helping students with homework, and the janitor took to reading in the lunchroom on his breaks to set a good example. Scores improved significantly, and the whole school benefited. It's possible to create that kind of school culture without dangling money in front of the staff. Most teachers are not in it for the money. But superior effort and performance should be rewarded and sub-par efforts penalized.

Merit pay bonuses, since they often rely on money from grants, corporate benefactors or other non-sustainable sources, are not a long term answer. Changing the pay system, as the Denver school system is doing, can be. Residents there believed so strongly that change was needed that they voluntarily raised their taxes by $25 million to fund the experiment.

In 2006, Denver schools allowed existing teachers to voluntarily enroll in ProComp, which replaces the traditional step system with one that uses a lower base plus bonuses awarded on the basis of nine separate measures of performance. The new system allows a teacher to earn as much or more than under the old pay scheme, and teachers willing to work in under-performing schools also get extra pay.

Measuring performance adequately, preventing favoritism and protecting teachers from unfair retribution are crucial to creating a performance-based salary scale that teachers support. So far Denver, which Obama and Education Secretary Arne Duncan have both used as an example, appears to have done that. Its system might be the right model for the next generation of teacher compensation systems. Obama thinks it could be, and more than half of Denver's teachers volunteered to work under the new system.

Change comes hard in New Hampshire, but a merit-based salary schedule in the state's schools should been seen as a question of "when," not "if."