When the woman’s voice comes over the intercom, the students are taking a test.

This is a lockdown drill, the voice says. Behave as if there is an active shooter in the halls. Do not leave the classroom until you are released. The woman sounds bored. Maybe it’s better that way, you think. An emotion would frighten the kids.

The students look at you. They’re juniors in high school. They’re worried about college applications and good grades. A few of them want to know if they can keep working on the test. You tell them “No.” You tell them to take a seat away from the window and the door. You tell them to hunker down and whisper. They ask you if they can keep their phones. You tell them “Yes.” You’ve learned that phones can be used as weapons. You can distract a shooter with a phone. Maybe you can blind him.

A student named Ashley turns off the lights. Ashley has worn the same Mamma Mia! sweatshirt for the last five days. You pretend not to notice. You pull down the shades. You sit in semi-darkness with the students and wait. A student asks you how long this will take. You tell the truth: “I don’t know.” The students text their friends. The students text their parents. Two girls do math homework together. You notice their sharp pencils. They could stab a shooter with those pencils, you think. They could draw blood.

You count your students and take attendance and realize that you still don’t know their faces. They’ve worn masks over their noses and mouths all year. They’re hair and eyes to you. They’re hand gestures and squints.

You read from the script you’ve been given. “Look around the room for weapons,” you say. “Think about what you could use to fight the shooter.” You try to sound bored like the woman on the intercom. You hand a student a hardbound dictionary and give another a stapler. A girl with green hair finds the brick the homeroom teacher uses as a doorstop. You give the “thumbs up” sign to the girl. She blushes and cradles the brick like it’s an infant.

You remember when one of your friends went through a lockdown drill the day before her maternity leave except no one said it was a drill. Your friend hid her swollen belly behind the teacher’s desk and tried not to cry. Two boys told her not to worry. “We got you, Ms. P,” they said. She cried anyway.

One of your colleagues wears a thick leather belt on lockdown days. He knows how to jam the door with his belt. You wonder if you should buy a man’s belt with a fat metal buckle. Maybe you could jam the door with a belt. Maybe you could strangle a shooter or use the belt as a whip.

Since the last school shooting, you carry sewing scissors in a plastic bag at the bottom of your backpack. Lately, you carry a “jogger fogger” too. You don’t sew or jog. You wonder if you could plunge the scissors into an active shooter’s eyes or neck. You would aim for soft spots; you would aim for spots the shooter couldn’t protect.

At Thanksgiving, that relative asked you if you would “take a bullet for the kids.” You stared at him without answering. He stared back. You wonder if he would take a bullet for one of his tax clients. You wonder if any of his teachers would’ve taken a bullet for him. You think you know the answer. You think he knows the answer too.

There’s a knock on the door. You’ve watched the safety films. You know what this means: You have to make a choice. The shooter will knock on the door. So will a lost child. The shooter is not a lost child. The shooter has a gun, but he will sound like a neighbor, a crush, a boy who played kickball in gym class. He will be none of those things; he will be all of those things. He will not wash his hands. He will not wear his mask. You must choose whether to unlock the door. If you make the wrong choice someone will die. If you make the right choice, someone will die too. This time you don’t answer the door. The stranger steps back into the hallway. A few seconds later, the knocking resumes. Someone else must decide.

A student asks for a mask because his nose is bleeding. You hand him three masks and a half-empty tissue box. A boy with skin the color of tapioca pudding points to a bottle of bleach. “That’s a weapon,” he says. “We could squirt that into the shooter’s eyes.” You agree that bleach is a good idea if the boy has good aim, if the shooter doesn’t wear glasses. The boy with the tapioca-colored skin snatches the bleach, and there’s giggling and backslapping.

The laughter is catching. It spreads from one student to another, a wild and wheezing secret. You hope some memory of their muffled snickering lingers in the deepest folds of their brains like a shared neural pathway long after this year. You think of the pink birthday balloon you lost so long ago, the way it bobbed above the gray cityscape far beyond your grabbing fingers. An unexpected bright dot vanishing and reappearing among the gritty clouds like a magic trick or a kiss.

“How much longer ‘til this is over?” asks the girl with green hair who is still holding the brick.

“We’re almost done. We’re almost done. We’re almost done.” This time the words bounce from your lips again and again like a spell or a chant, like a pledge you could actually believe.