June 3, 2015 11:31 AM EDT

Police arrested two seventh-graders in a Belgrade, Serbia suburb on Tuesday, after the pair—clad in balaclava masks and sunglasses—entered their classroom armed with a knife and plastic replica handgun and stole their teacher’s grade book.

A police officer who asked to remain unnamed told Reuters that the act was carried out in agreement with a third student, who was looking to have the record of his poor grades removed.

The two students face charges including violent behavior and jeopardizing public safety.

Serbia has seen notably high rates of school violence since the Yugoslav Wars of the 1990s. In 2005, UNICEF established a “School without Violence” program in the country, responding to a study conducted by The Institute for Psychology at the Belgrade Philosophy Faculty, which found that 65% of students across 54 schools in Serbia reported having been affected by violent behavior in schools.

[Reuters]

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