(CNN) -- Thirty-four schools in New Jersey are being investigated for possible cheating after an examination of standardized test data revealed irregularities and raised questions, the state Department of Education said.

State education officials said some schools showed especially high deviations from the normal amount of wrong test answers being erased and a right one marked.

Since 2008 the New Jersey Department of Education has had the state's assessment contractor, Measurement Inc., provide reports on erasure patterns at schools and at each grade level. These reports show the number of times answers on standardized test forms are erased and changed.

The 34 schools now under investigation showed erasures from wrong to right two to five times as often as the state average, state school officials said. According to the reports, 25 district and charter schools were found to have these high averages in at least one grade level, while nine schools had abnormally high levels of erasure schoolwide.

In numerous U.S. cities, including Atlanta, Philadelphia and Washington, accusations and findings of test cheating being condoned and organized by teachers to make their schools look better have put the issue in the national spotlight, and prompted education officials across the country to re-examine testing procedures and protocols.

New Jersey's acting education commissioner, Christopher Cerf, noted those incidents in a memo sent to all districts and charter schools on Tuesday.

"The recent wave of cheating scandals across the country has reminded us that even though the vast majority of our teachers and administrators are honest, hardworking professionals, a small handful of unethical people sometimes do unethical things," Cerf wrote Tuesday.

But, he insisted, "in no way do these reports prove that cheating occurred, nor do they implicate any school or teacher in wrongdoing,"

"High instances of erasure marks, where wrong answers are changed to right answers, happen for many reasons, including students checking their work or students making mistakes in tracking their test with the answer folder," he wrote.

All told, 120 schools registered higher erasures than the state average, according to the reports. The percentage of erasures from wrong to right was 58.5% in 2010, higher than the 56.9% in 2009. In his memo however, Cerf asserted, "In conversations with testing experts, we believe these results to be in line with trends across the country."

"By themselves these numbers tell us nothing," said Justin Barra, director of communications for the state Education Department. "This is one data point that we use to investigate schools for wrongdoing."

Barra explained that a combination of the test data, unannounced classroom observations, tips, and other investigations is the best way to maintain secure and accurate testing data and to catch potential cheaters.

As a result of standard oversight, the test erasure data and tips from other teachers and concerned parents, eight instructors were found guilty of breaching protocol last year, according to Barra. Of those eight, two worked at schools among the 34 highlighted in the reports.

The investigations into possible wrongdoing are expected to be wrapped up in August, according to the Department of Education.

In his note Tuesday, Cerf wrote, "We will continue to be vigilant in monitoring potential testing irregularities and acting with the full authority of the department when we find an infraction."