State investigators found suspicious patterns of changed answers on tests at Philadelphia's Roosevelt Middle School

When one seventh-grade student at Philadelphia's Roosevelt Middle School took state reading and math exams in 2009, answers were erased 35 times - changed from wrong to right every time.

The odds of that happening naturally are more remote than 1 in 100 trillion. Winning the Powerball lottery, whose odds are still an astronomical 1 in 195 million, is much easier.

Eighty-two students at Roosevelt - one-quarter of the school's seventh and eighth graders tested - had statistically suspicious patterns of changing answers on state tests in 2009, state-appointed investigators have found.

The East Germantown school - hailed by Superintendent Arlene C. Ackerman last year as a district pacesetter - came under scrutiny in May after several Roosevelt teachers told The Inquirer that they had witnessed deliberate test security breaches there in the last few years.

The teachers said they had seen answers written on a blackboard, students being given improper assistance, and other violations.

A subsequent Philadelphia School District investigation of 2011 testing in the spring found no proof of improprieties at Roosevelt. The inquiry did not involve an analysis of erasures or other statistical measures.

The 2009 investigation, based on an in-depth analysis of multiple indicators by Data Recognition Corp. of Minnesota, surfaced a few days later after sitting on a shelf in the state Education Department for two years.

After learning of its contents, Ronald Tomalis, the new state education secretary, asked districts where school tests had been flagged to look into the matter and report back to him. And he ordered similar statistical studies of 2010 and 2011 state tests.

An analysis by The Inquirer of the 2009 report's student-level data found that some Roosevelt students' ability to fix their wrong entries was uncanny.

Nineteen students had nearly perfect erasure patterns - at least nine out of 10 times they adjusted an answer from wrong to right. Six of the students were perfect on such fixes.

This is the sort of performance that in just two years lifted the school's test scores a stunning 52 points in math on a 100-point scale and 51 in reading on the state tests. The improvement was the best - by a considerable margin - of any comparable school in the district.