I would list all the trigger warnings that might apply to the story, but really, the opening paragraph lays it all out:
"The drakeela hid in the cloakroom during recess. It didn’t like fresh air, and of course the sun was poison to its kind: they all knew that, even Lucy who wasn’t allowed to watch the Sunday Monster Movie and had to be told what a drakeela was. At 10:30 a.m. the bell rang, and Mrs. Shelby said line up everyone. Mrs. Shelby looked up and down the line and wiggled her fingers as though she were counting. But she never counted the drakeela as it crab-crawled between the fluorescents over the art tables and twanged its thick dark fingernails on the sheet-metal ductwork that hung over the make-believe kitchen."