The grainy cellphone video, which was shared across several social media accounts, showed Mariana and the other girl fighting, and the officer between them, trying to pry them apart. After he broke up the fight, he grabbed Mariana and lifted her up, then slammed her to the ground.
She laid on the ground for several moments as the crowd broke up.
Mariana told NBC DFW that the fight began after the other girl made fun of her.
The Dallas Independent School District issued a statement saying that officials received word of the video being shared on social media the day after the fight.
"The video…captures a Dallas ISD police officer who attempts to end the disruption, however, his actions do not appear to represent the type of response we want our officers to display," the statement said, according to NBC DFW. "The officer has been placed on administrative leave while we conduct a thorough investigation."
Valadez told the news station that leave is not a sufficient punishment.
“I don’t want him being suspended, I want him fired,” she said. “Why is he still working with kids? He’s not capable of working like that.”
The school district said it is uncertain if the officer would return to his job.
Mariana returned to school Tuesday after serving a three-day suspension, the news station reported.