In Camden, N.J., a principal said the pressure to pump up students' standardized test results came with a threat from a district supervisor — nice medical benefits you have for your sick daughter, sure would be a shame to lose them.

In Atlanta, one school's test booklets showed such a brazen pattern of doctoring, a security expert estimated that the probability of that happening by chance was one in 10 to the 52nd power.

Across the country, in city and suburban schools, in large and small districts, teachers and other staff members have been accused of sharing test questions in advance with students, watching over their shoulders as they take tests to point out wrong answers, and correcting mistakes after the fact — all to inflate scores and satisfy federal and state mandates for achievement gains.

This week, Baltimore school officials said staff members at two elementary schools had erased wrong answers and replaced them with correct ones on Maryland School Assessment booklets in 2009 and 2010, helping to boost math and reading proficiency scores. Last year, another city elementary school was found to have altered MSA tests in 2008.

The cheating scandals have put the spotlight on standardized tests used to measure progress under the No Child Left Behind Act, which ties federal education funding to schools meeting certain benchmarks. Increasingly, tests are also being used to evaluate the performance of teachers and principals, determining how much they are paid and whether they remain in their jobs.

"The tests now are high stakes. You could lose control of your schools," said John Fremer, a test security consultant who has investigated cheating allegations in numerous school districts across the country. "You raise the stakes, you get more cheating."

Fremer, however, is among those who believe that for all the attention that cheating scandals get, they represent a tiny fraction of all testing, perhaps 1 or 2 percent. Similarly, State Superintendent Nancy S. Grasmick characterized the tampered test results at Abbottston and Fort Worthington elementary schools as "minuscule" compared with the thousands of exams that are administered cleanly every year.

But the impact of a cheating incident can be outsized, casting a shadow of suspicion on an entire district and its legitimate progress. As a result, the 2011 MSA exams, whose scores will be announced next week, were administered under extraordinary security measures. Outside monitors watched as tests were opened to be distributed and then sealed after students completed them. The tests were stored in tamper-proof boxes under lock and key until collected by state officials.

And next year, Grasmick said, every booklet will be reviewed.

The need for verifiable test results has led to an entire industry devoted to analyzing results: checking for excessive erasures, for example, especially when the changes always make wrong answers into correct ones. Or, said Fremer, president of Utah-based Caveon Consulting Services, a batch of tests could show that every child had the same wrong answer on one question.

Educators say they are not surprised to learn of incidents of cheating, given the rising importance of test scores — often to the exclusion of other forms of assessing how students, teachers and schools are doing.

"Everyone is caught up in this mania for standardized testing," said Diane Ravitch, an influential researcher and writer on education. "Good people get caught up in bad things. They're putting pressure on principals and teachers … to do all the wrong things."

Ravitch, a professor at New York University, has reversed course on the subject of standardized testing, having previously supported it as a means of accountability. Now, said the former assistant education secretary in President George H.W. Bush's administration, the tests have become too important, crowding out other measures of the quality of education.

Daniel Koretz, author of the book "Measuring Up: What Educational Testing Really Tells Us" agrees.

"Evaluations rest almost entirely on test scores," said Koretz, a professor at the Harvard Graduate School of Education. "Nothing else counts, or if it does, it doesn't count for much."

Koretz said performance targets set for schools can be arbitrary, and teachers don't get enough support to help achieve them. Even if school personnel do not succumb to the temptation to cheat, said Koretz, the focus on testing means that too much classroom time is spent trying to "game" the system in other ways.

And that is fairly easy to do, he said. Teachers and other staff can easily figure out from previous years what areas the test will cover, the kinds of questions likely to be asked and even how they will be phrased — and concentrate their efforts accordingly, he said.

As a result, he said, even schools with high test scores are producing students with glaring gaps in their knowledge. Some of the kids who passed their state's assessment tests with flying colors, he and Ravitch pointed out, arrive in college needing remedial work in basics such as math and reading.

Maryland moved last week to begin evaluating teachers based in part on how well students learn their lessons — though the plan was opposed by teachers. The new system, crafted by a gubernatorial task force, will start as a pilot program In Baltimore, Baltimore County and five other districts this fall, and part of teachers' job rating will be based on students' results on state tests.