The city performed what it calls an "aggressive" analysis of test score irregularities at 18 classrooms from last year's D.C. CAS exam.
A school official said no widespread evidence of cheating was found. Nearly 3,800 classrooms take the test each. A preliminary investigation into the integrity of this year's results found 31 irregularities, 14 of which will require further action by the office.
Officials released some examples of what qualified as test security violations. In one case, an entire class was given last year's exam by the teacher to practice with. In another case, a student finished the exam in half the time of other students and later told investigators he or she was familiar with the questions.
Officials say, in the wake of the analysis, they've issued tighter security guidelines and doubled the number of schools being monitored for testing irregularities.