The District is invalidating standardized test scores of 18 testing groups at 11 schools after “serious test security violations” were discovered, signifying that cheating likely occurred at the schools, officials announced Friday.

The D.C. Office of the State Superintendent of Education hired the consulting firm Alvarez and Marsal to look at 2012 math and reading scores on the D.C. Comprehensive Assessment System (CAS) standardized tests across all 243 public schools.