ATLANTA (AP) — Students at Apalachee High School outside Atlanta will return to campus for half-days beginning next week, Barrow County school officials announced, after a Sept. 4 shooting that killed four people and injured nine others.

Emergency calls to 911 during Georgia’s Apalachee High School shooting rose so rapidly that some people had to wait on hold to speak to a dispatcher, newly released records show. Barrow County Emergency Communications struggled to keep up with the flow of calls around 10:20 a.

Bomb threats, copycats, and pranks—some from outside the United States—have disrupted schools across the nation.