After months of investigating, Dallas ISD says someone changed answers on standardized tests after Lang Middle School students turned in their exams.

Now some are wondering whether the district's pay-for-performance program might tempt educators to cheat.

"Certainly it's a concern, and certainly that's a possibility," DISD spokesman Jon Dahlander said. "But at this point ... it's too early to say whether that was the driving factor."

All Lang Middle School eighth-graders were asked to retake part of their Texas Assessment of Knowledge and Skills test in the summer after DISD noticed "testing irregularities." About 36 percent fewer students passed after the second round of testing.

It's still unclear who is responsible for altering the eighth-grade tests at Lang. The school's former principal and test coordinator have resigned, and officials say they have not cooperated in the investigation. DISD says the tests were not properly secured overnight.

Dale Kaiser, president of the National Education Association-Dallas, said he worries test-related incentive pay could lead to cheating.

"Anytime you dangle that amount of money that the district has dangled in front of people, you will have those who find a way to cheat," he said.

Between federal, state and district funds, Dallas teachers can receive up to $8,000 in incentive pay for high performance. Principals can receive more than $10,000.

Some say the problem is the emphasis on test scores to determine performance. For example, Kaiser said, 60 percent of principals' evaluations are based on test scores.

"You have the carrot — the money — and the stick — getting fired — working on all of our educational personnel," Kaiser said. "They need to focus on educating the students."

State Sen. Florence Shapiro, R-Plano, defends her support of state incentive pay for educators.

"It's a way to incentivize and appreciate good teachers and principals in the system," said Shapiro, chair of the Senate Education Committee.

But Kaiser said he wants to see a revamped incentive pay system that de-emphasizes test scores.

"Let's develop something that will accurately reflect how our students achieve, without the focus on test scores."