I stood at my locker with Becky and Lia, the two of them chatting about a TV show they watched last night. I laughed along, even though I hadn’t seen it, just enjoying the way we were joking before class. The hallway was buzzing with noise—shoes squeaking on the tiles, lockers slamming, students calling out to each other as they hurried to class.

Then the bell rang, sharp and loud, echoing down the hall. My chest tightened instantly. I hated being late, so I spun to my locker and fumbled ...