Meridian Public Charter School has begun an internal investigation into cheating on standardized tests after a District investigation found "strong circumstantial evidence" that cheating efforts were orchestrated throughout the school, officials announced Monday.

Standardized tests across the school had 1,804 wrong answers erased and changed to right answers last year, one of the highest levels of changed answers in a single public school in the District, according to the investigation by the Office of the State Superintendent of Education.

A fourth-grade teacher at the school and that teacher's proctor suggested students rethink answers on questions they got wrong, according to the findings. A fifth-grade teacher told investigators he helped students with difficult words in questions.

Schools with test violations
Critical violations -- test tampering or academic fraud
Beers Elementary School
Brightwood Education Campus School
Hendley Elementary School
Kenilworth Elementary School
Langdon Education Campus School
Miner Elementary School
Winston Education Campus School
Arts and Technology Academy Public Charter School
Community Academy Public Charter School's Amos 1 Campus
Imagine Hope Community Public Charter School's Lamond Campus
Meridian Public Charter School
Moderate violations -- violations, but not test tampering
Eaton Elementary School
Mary McLeod Bethune Day Academy Public Charter School
National Collegiate Preparatory Public Charter High School
William E. Doar Public Charter School for the Performing Arts
Minor violations -- test administration errors
E.L. Haynes Public Charter School

In addition to hiring Arent Fox LLP to conduct an internal investigation into OSSE's findings, the school has removed last year's test chairman and the five teachers and five proctors who were flagged from administering this year's Comprehensive Assessment System, which began Monday, said school Board Chairman Christopher Siddall. The school has increased security of test booklets, forbidden teachers from administering tests to their own classes and hired Ten Square LLC to assist with security.

Cheating has been a problem in the city since shortly after the school system began using students' performance on standardized tests to determine whether teachers get raises, earn bonuses, or even keep their jobs.

Meridian was one of 11 schools -- four charters and seven traditional public schools -- with "critical" test security violations and one of 16 with some type of violation or anomaly in the report OSSE released just over a week ago.

Teachers were reported assisting students during testing by explaining questions or suggesting students reconsider answers at 12 schools, including Meridian.

At Langdon Education Campus, a teacher overseeing three second-grade special education students was seen sitting at a student desk with a student's test booklet in her lap. "There was nothing on the student's desk," the DCPS observer reportedly told investigators.

Teachers at Langdon also reportedly allowed students to take home copies of that year's CAS booklets to practice with before the test in each of the last several years, including 2012, and five test booklets disappeared after testing was over, according to the OSSE incident report.

At Mary McLeod Bethune Day Academy Public Charter, one teacher claimed that a second teacher taught his class to use hand gestures to communicate test answers, then used those hand gestures during the test administration. School officials did not return requests for comment.

Only the 18 classrooms across the city with critical violations -- in the case of Meridian, for example, the five classrooms flagged for signs of cheating -- had their test scores invalidated, OSSE said.

DCPS' new security measures were used Monday during test administration, and any people named in OSSE's investigation were barred from testing procedures, said spokeswoman Melissa Salmanowitz.

"We take test security incredibly seriously," she said. "When instances of cheating are confirmed, we move swiftly to take the appropriate personnel action. We are conducting a review of the OSSE's findings and will make determinations about their 2012 findings and terminations accordingly."