Dozens of Texas schools appear to have cheated on the state's redesigned academic achievement test, casting doubt on whether the accountability system can reliably measure how schools are performing, a newspaper found.

An analysis uncovered strong evidence of organized, educator-led cheating on the Texas Assessment of Knowledge and Skills (search) at schools in Houston and Dallas, along with suspicious scores in hundreds of other schools, The Dallas Morning News reported.

Texas education policies on student accountability became the model for the federal No Child Left Behind (search) law enacted after President Bush's election in 2000.

The newspaper analyzed scores from 7,700 Texas schools, searching for ones with unusual gaps in performance between grades or subjects. It said research has shown that schools that are weak in one subject or grade are typically weak in others.

More than 200 schools had large, unexplained score gaps between grades or between the TAKS and other standardized tests, such as the Stanford Achievement Test.

It found, for example, that the fourth-graders at Sanderson Elementary School in the Houston Independent School District scored extremely poorly on the math TAKS test this year, rating the school in the bottom 2 percent of the state.

However, the school's fifth-graders ended up with the highest scale scores on the math TAKS of any school in Texas, with more than 90 percent of the students getting perfect or near-perfect scores.

Houston Superintendent Abe Saavedra said he has asked the Texas Education Agency to investigate the scores at Sanderson, which the U.S. Education Department named a Blue Ribbon School in 2003 because of rapid improvements in test results.

"At HISD, our credibility and integrity must remain absolutely beyond question," he said in a statement.

Similar results were found at Harrell Budd Elementary in Dallas. Third grade students finished in the bottom 4 percent in reading. But Budd's fourth-graders had the second-highest reading scores in the state, behind a Houston magnet school for gifted children.

Dallas district spokesman Donald Claxton said officials there plan a thorough investigation.

"If there's cheating going on, we want to stop it," he said.

Jim Impara, a former state assessment director in Florida and Oregon, said he believes such school rating systems are changing the culture of education.

"When you have a system where test scores have real impact on teachers' lives, you're more likely to see teachers willing to cheat," he said.