Fairfax County Schools Superintendent Karen Garza was a key figure in the implementation of a controversial teacher evaluation and merit pay system that is now the focus of a federal lawsuit filed in Houston last week.

Garza, who joined Fairfax County in July, was the second-in-command of the Houston Independent School District from 2005 to 2009. As chief academic officer, Garza was responsible for leading the rollout of Houston’s program that aimed to evaluate teacher effectiveness, known as the “Educational Value-Added Assessment System.”

The program involved rating teachers based on their students’ test scores, which are used to determine pay raises, bonuses and whether the educators are promoted or fired. Such “value-added measurements” are popular with school systems around the country and have gained new prominence with the support of the Obama administration, but teachers and teachers unions have railed against the programs, saying they unfairly weight student test scores in their evaluations.

On Wednesday, the Houston Federation of Teachers filed a lawsuit in U.S. District Court for the Southern District of Texas against the Houston school district, alleging that the teacher performance system is “inaccurate and unfair.”

“The absolute absurdity lies in the concept of whether or not a child learns is based on the teacher,” said Gayle Fallon, president of the Houston Federation of Teachers. “Really? So poverty has nothing to do with it? Conditions at home have nothing to do with it? According to this, it’s 100 percent the teacher. It defies logic.”

In Fairfax, student achievement accounts for 40 percent of a teacher’s evaluation, said Steven Greenburg, president of the Fairfax County Federation of Teachers. Standardized test scores are part of the overall evaluation, but multiple factors also are considered.

Fairfax County experimented with a performance pay system from 1986 to 1992, and some teachers received $4,000 in bonuses. But Fairfax dropped the program after schools officials found it “politically problematic,” a schools spokesman said in 2008.

Greenburg said that when Garza arrived in Fairfax, he mentioned her previous involvement with the controversial merit-pay system in Houston.

“She assured me that she had no intention of leading in that direction in Fairfax County,” Greenburg said. “She immediately came back with, ‘Don’t worry about this, it’s not something I’m looking to do.’ ”

Through a spokesman, Garza declined to discuss her opinions on value-added measures in Houston or their possible viability in Fairfax. She also declined to address the Houston lawsuit.

“Because it has been five years since I was in Houston, I fear that any comment I would make would no longer be relevant,” Garza said in a written statement to The Washington Post last week.

Fallon, of the Houston teachers union, said Garza was responsible for implementing the new system there in 2006. The system, which relies on a complex mathematical formula, was used to calculate bonuses for teachers based on student test scores.

Some teachers earned more than $8,000 in extra pay, while others earned bonuses of less than $10, Fallon said. But few understood how the complex bonus system worked.

“Teachers said it was like winning the lottery,” Fallon said. “They didn’t have a clue what they had to do to get it.”

By 2011, Houston schools administrators had begun using the system to determine whether teachers should keep or lose their jobs, Fallon said, noting that the lawsuit seeks an end to that practice.

Fallon said Garza was among the Houston administrators responsible for explaining the new measures to teachers.

Garza acknowledged the system was controversial in written testimony to the Texas state senate in 2008. Garza wrote at the time that the Houston teacher performance methodology “has been scrutinized for its lack of transparency and complexity.” She also said publicly that her administration stumbled in the new system’s rollout, which was met with anger among teachers who complained that the system was unfair, according to a 2009 Houston Chronicle report.

But in testimony to the Texas state senate education committee that year, Garza advocated for statewide adoption of the value-added method Houston was using.

“We have embraced value-added methodology, which we believe provides a much more in-depth analysis of teacher, campus and district effectiveness,” Garza said, according to a transcript of the testimony. “For these and many other reasons, we strongly implore the committee consider a value-added model such as EVAAS.”

The district revised its formula in 2010 to emphasize teamwork among teachers and taking more data into account, according to the Chronicle.