The footage appears to show a female student striking instructor Tiffani Shadell Lankford, who then appears to repeatedly punch the girl, slam her to the ground, then stomp on her head, according to the Hays County Sheriff's Office.
Lankford, 32, was immediately fired by school officials, who called authorities. "There is absolutely no excuse or circumstance that can justify what you see unfold on the video," Tim Savoy, a spokesman for the school district, said in a statement. "It is unconscionable what this adult did to one of our students."
The alleged incident took place in a Spanish class Lankford was teaching. She began working for the district in August and taught her first class in September, school officials said.
She was arrested Friday and released on a $10,000 bail, online records show. It was not clear if she had retained an attorney.
The 15-year-old student, a sophomore, has epilepsy and was being treated at a hospital for severe injuries, according to CBS News.
A fellow student said the teacher became upset when students started laughing during class. "Me and a group of friends were all laughing," the girl, who did not want to be identified, told reporters. "It was just a joke somebody said."
The injured student's family attorney issued a statement. "This is unacceptable to say the least, and we will demand justice to the fullest extent of the law" the lawyer said.