Houston is about to become the biggest school district in the nation to tie teachers' pay to their students' test scores.

School Superintendent Abe Saavedra wants to offer teachers as much as $3,000 more per school year if their students improve on state and national tests. The program could eventually grow to as much as $10,000 in merit pay.

The school board is set to vote on the plan Thursday. Five of the nine board members have said they support it.

"School systems traditionally have been paying the best teacher the same amount as we pay the worst teacher, based on the number of years they have been teaching," Saavedra said. "It doesn't make sense that we would pay the best what we're paying the worst. That's why it's going to change."

Opponents argue that the plan focuses too much on test scores and would be unfair to teachers outside core subjects.

Other school districts have adopted such programs in recent years. Denver, with 73,000 students, took such a step in November, becoming the biggest district to do so. Houston, with more than 200,000 students, is the nation's seventh-largest district.

Denver's program and others measure teacher performance not just on standardized test scores, but also on their subject certifications and other factors.

Traditionally, Houston teachers' experience and education levels have determined their pay scale. Starting teachers make about $36,000 a year. Salaries can rise to about $45,000 with advanced degrees and more experience.

Texas has no collective bargaining, meaning the teachers union can lobby the district for raises but cannot strike.

The Houston Federation of Teachers feels the plan is being forced on employees, said Gayle Fallon, the union's president.

"This plan is nothing but test scores," she said. "It's not well thought-out."

But for Monica Ramirez — a kindergarten teacher for Spanish-speaking students and the district's teacher of the year in 2004-05 — merit pay is an incentive.

"If we are not motivated, we cannot motivate our children," she said.

The plan is divided into three sections, with as much as $1,000 in bonus pay each.

The first would award bonuses to all teachers in schools rated acceptable or higher, based on scores on the state's main standardized test. The second ties pay to student improvement on a standardized test that compares performance to nationwide norms.

In the third section, reading and math teachers whose students fare well compared with others in the district would be eligible for bonuses.

Bonuses for all sections will be given only if students show improvement in the top half of scores.

Fallon said the plan is unfair to teachers in such subjects as art and music.

Saavedra expects the plan to cost $14.5 million the first year and increase by $8 million each year for the next five years. He said there are no plans for a tax increase to pay for it.