The movie was heavily promoted as a thriller in trailers, posters and other media, but some critics found it misleading, since fits most in the drama category due to its content.
A group of private secondary schoolgirls have to remain in their classroom and wait for the police to arrive and interrogate them, since they all are suspects of something terrible that had just happened at their school.
The movie begins as the initial narrator quietly sits in the back of the classroom, separated from the rest, while the others simply ignore her.
Previously, around 2008, there was a stage play of Perras written by Guillermo Ríos with the following cast: The movie has received mixed to bad critics.
The critics questioned mostly the participation of adult women as the main characters, playing as secondary school girls, instead of casting true teenage actress (a common practice in Mexican TV shows), and the frequent and unnecessary allusions to old Mexican soap operas and some connotations not according to the age the main characters supposedly have.