It's not that Saira is unfit or out of shape by normal standards. At the mundie school her parents forced her to attend, back home in Karachi, she was, through great effort, solidly middling in gym class.

Physical skills have never come easily to her, her body always slower and clumsier while her mind raced ahead. She didn't walk until she was nearly two, which terrified her parents, but she was casting her first baby spells at a much younger age than most wizard kids. She loves studying magic, learning languages, and reading books on every other academic subject she can get her hands on. Studying is easy, and usually fun. Exercising is difficult, frustrating, and boring, which makes it excellent for mana-building but did not exactly motivate her to put in the hours to persuade her reluctant body to get good at anything. Mediocre is fine. Mediocre lets you run away from mals. 

Except that now she's in the Scholomance, where being able to run away from mals faster than everyone else is a survival skill, and most of the other people here have spent much longer than her in this meat grinder of natural selection. A few months into term, most of the people even less prepared than her have already been picked off, and "mediocre" is starting to look like "bottom of the pack". 

There's this English saying she read in a book somewhere: "You don’t have to run faster than the bear to get away. You just have to run faster than the guy next to you." Saira can run faster than the mals, mostly. But, when a nest of skittering creatures come boiling out of the supply cupboard, everyone else in her Intro to Shop class can run faster than her.

An enclaver with Saira's abilities would be fine. Her aptitude as an incanter would make her valuable enough for her clavemates to protect her at their own expense, or recruit desperate indies to be her human shields. But Saira isn't an enclaver, and she's not good at making friends or sucking up to powerful people—another skillset she neglected because it was harder and less rewarding than academics—and she hasn't found an opportunity to get in with a group for protection yet. For now, she's on her own, surviving on that knife edge where one stumble can be deadly. 

She stumbles, and her flailing arm knocks somebody's half-finished artifice off the workbench—