Houston became the largest school district in the country on Thursday to adopt a merit pay plan for teachers that focuses on students’ tests scores.

By a 9-0 vote, the Houston school board approved a plan that offers teachers as much as $3,000 in extra pay if their students improve on state and national tests. The program could be expanded to provide as much as $10,000 in merit pay for teachers.

The vote came after several teachers told the board at its monthly meeting they believed the plan was flawed and unfair because some teachers will be eligible for larger bonuses than others.

“This is not a perfect plan, but it is a beginning,” said school board president Diana Davila.

Other school districts nationwide have implemented various types of incentive pay programs for teachers in recent years. Denver adopted one in November, becoming at the time the largest district to do so. Houston, with more than 200,000 students, is the nation’s seventh-largest district.

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

The first will 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.

Teacher Kim Hemmis reads a book to her first grade class Wednesday, Jan. 11, 2006 at Will Rogers Elementary School in Houston. Student performance could soon be the main factor that decides which teachers make the most money in the Houston school district. Superintendent Abe Saavedra is proposing a new incentive pay plan that would offer teachers up to ,000 more in salary if their students show improvement on state and national tests. (AP Photo/David J. Phillip)

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

The teachers’ union doesn’t approve of the plan, saying it focuses too much on test scores and is too complicated.

“Any time you divide one set of teachers from another, you are sending the wrong message,” said Jana Angelov, a high school art teacher who has been with the district for eight years.

Ben Hernandez, 30, a kindergarten teacher who helped design the plan, said that even though he does not like the focus on test scores, he believes the plan will be a good way to reward teachers for hard work.

“If I am to continue to be successful as an educator, I must change,” he said. “The system must change also. This proposal is a change from the past, a change for the better.”